- Email: [email protected]
Portal Venous Gas and Pneumatosis Intestinalis; Radiologic Signs with Wide Range of Significance in Surgery
ORIGINAL REPORTS
Portal Venous Gas and Pneumatosis Intestinalis; Radiologic Signs with Wide Range of Significance in Surgery Nader Naguib, MD, MRCS,* Peter Mekhail, MRCS,* Vivek Gupta, FRCS,* Nagy Naguib, MSc,† and Ashraf Masoud, FRCS* *Department of Surgery, Prince Charles Hospital, Merthyr Tydfil, United Kingdom, and †Department of Radiology, Johann Wolfgang Goethe University Hospital, Frankfurt, Federal Republic of Germany BACKGROUND: Portal vein gas (PVG) was described as an uncommon ominous radiologic sign usually harboring an intraabdominal catastrophe. When accompanied by pneumatosis intestinalis (PI), it is more predictive of bowel ischemia. Since the wide use of computed tomography (CT), both signs could also be viewed as incidental findings during routine radiologic investigations. METHODS: We present a series of 12 cases that showed either
or both signs, collected in a district general hospital between 1991 and 2011. RESULTS: The diagnoses in these cases varied between fatal bowel ischemia and the mere presence of radiologic signs in the absence of significant pathology. CONCLUSION: PVG and PI are radiologic signs that can
represent a wide range of pathology. (J Surg 69:47-51. © 2012 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.) KEY WORDS: portal venous gas, pneumatosis intestinalis
were reported, increasing the total number in literature to approximately 335 cases.5 In approximately 50% of the cases, PVG is associated with pneumatosis intestinalis (PI), gas within the bowel wall.6 Knechtle et al.7 described PI first in 1730 during postmortem dissection, more than 2 centuries earlier than the description of PVG and with a far greater number of cases in the literature (350 by 1990). PI has 2 forms: Primary PI is rather a benign condition with submucosal or subserosal cysts in the colon, and secondary PI with circumferential or linear air affecting any part of the gastrointestinal tract.8
METHODS The data were extracted from the computerized radiology database using the following search terms: “portal vein gas and/or air” and “pneumatosis intestinalis” between 1991 and 2011. The computed tomography (CT) service was introduced in the hospital in March 1991. Subsequent details on each case were obtained from clinical portals and theater database. A statistical analysis was performed using the Fisher exact test.
COMPETENCIES: Patient Care, Medical Knowledge, Practice
Based Learning and Improvement
RESULTS
INTRODUCTION
In 20 years, a total of 12 cases were identified (7 men and 5 women) with a median age of 66.5 years (range, 29-80 years). Six cases were identified by CT abdomen, 3 cases were identified on plain abdominal X-ray (AXR), 2 cases were identified incidentally on barium enema (BE), and 1 case was found incidentally on abdominal ultrasound examination. Both radiologic signs were present together in 5 cases (Fig. 1). PVG only was reported in 4 cases (Fig. 2), and PI only was reported in another 3 cases (Fig. 3). A breakdown of all cases is shown in Table 1. Six patients underwent laparotomy for an acute abdomen; 5 of them had both signs of PVG and PI on CT scan. Again,5 of these 6 patients had ischemic bowel and underwent resection of the ischemic segment. The sixth patient had a negative laparot-
Portal vein gas (PVG), which is the presence of air in the portal venous system, is a radiologic sign first described in 1955 by Wolfe and Evans1 in 6 neonates who died of bowel ischemia. The sign was described first in adults in 1960, by Susman and Senturia,2 but the first survivor with this sign was reported by Lazar in 1965.3 Liebman et al.,4 in 1978, reported mortality rate of 75% associated with this sign after collecting all 64 cases in the literature. Between 1975 and 2008, another 275 cases Correspondence: Inquiries to Nader Naguib, MD, MRCS, Department of Surgery, Prince Charles Hospital, Merthyr Tydfil, United Kingdom CF47 9DT; fax: ⫹⫹441-1685728126; e-mail: [email protected]
Journal of Surgical Education • © 2012 Association of Program Directors in Surgery Published by Elsevier Inc. All rights reserved.
1931-7204/$30.00 doi:10.1016/j.jsurg.2011.07.005
47
FIGURE 3. CT scan showing pneumatosis intestinalis.
FIGURE 1. CT scan showing portal venous gas and pneumatosis intestinalis.
omy with no surgical explanation offered for the patient’s symptoms and the associated PVG and PI. Four patients had incidental radiologic finding of PVG and/or PI; 2 found on a barium enema, 1 on an abdominal ultrasound, and 1 on AXR after a colonoscopy. Two patients were admitted to the hospital unwell and died shortly after. One had PVG and small bowel obstruction on AXR. The other had PI, and postmortem examination revealed drug overdose.
FIGURE 2. CT scan showing portal venous gas. 48
The overall mortality rate was 41.7% (5/12). Of the 7 patients who survived, 4 demonstrated PVG and/or PI while being investigated for a separate problem and were considered incidental findings (4/12). Only 3 patients survived among the remaining symptomatic 8 cases (not incidentally found), for a mortality rate of 62.5%.
DISCUSSION PVG and PI usually were described in the literature as separate entities, although both were described as ominous signs and were found to share the same etiologic factors and pathophysiologic mechanisms. It has been presumed that PI ascends from the draining venous mesentery and condenses in the portal venous system,9 so they should be considered as progressive steps in a single process.10 PVG is associated with PI when the intraluminal gas finds its way into the mesenteric veins, and if the gas does not reach the veins, then PI will be present alone. Occasionally, intraluminal gas may enter the portomesenteric veins directly without producing a radiologically detectable pneumatosis.6 Again, in the literature, the etiology for either signs was generally classified into (1) ischemic gastrointestinal disease, (2) nonischemic gastrointestinal disease, and (3) pulmonary disease.5,8 Bowel ischemia is the most common cause (61%) and carries a poor prognosis with associated mortality of 75% to 90%.4,5,6,10-12 In our study, the mortality rate associated with bowel ischemia was 40% (2/5). However, noncritical causes can lead to these signs; ie, the finding of PVG and/or PI may just be an incidental finding and does not warrant surgical intervention. These causes include diagnostic gastrointestinal procedures (eg, endoscopy and barium enema), trauma, chemotherapy, immune suppressants after transplantation, and idiopathic causes.5,7,13 The iatrogenic and idiopathic causes for PVG were reported as 3% and 1.8%, respectively.5 The 2 main hypotheses explaining the occurrence of these radiologic signs are the mechanical- and bacterial-derived ori-
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
TABLE 1. Clinical Breakdown of the Cases PVG
PI
Age
Sex
1
Yes
Yes
80
F
2
Yes
Yes
74
3
Yes
Yes
4
Yes
5
Radiology
Survived
Diagnosis
CT
Yes
M
CT
Yes
67
M
CT
Yes
Yes
66
F
CT
No
Yes
Yes
71
M
CT
No
6 7 8
Yes No No
No Yes Yes
65 68 29
M M F
CT AXR AXR
No Yes No
9
Yes
No
64
M
AXR
No
10
Yes
No
63
F
BE
Yes
11
No
Yes
72
F
BE
Yes
12
Yes
No
32
M
U/S
Yes
Afferent loop ischemia after partial gastrectomy and Roux en Y anastmosis. Refashioning of the anastmosis was performed Ileal loop ischemia. Patient had resection and exteriorization of both ends. Small bowel obstruction and bowel necrosis. Laparotomy; resection and primary anastomosis Acute surgical abdomen, bowel necrosis. Laparotomy; resection and primary anastomosis Abdominal pain on day 6 postgastrectomy; increased lactate. Negative laparotomy. Small bowel obstruction, bowel necrosis on laparotomy. Incidental finding after a colonoscopy, no action required. Died in ITU same day, postmortem showed drug overdose and pulmonary oedema. Rectal cancer, Small bowel obstruction, died shortly after admission. Incidental finding at the barium enema during large bowel investigation, no action required. Incidental finding at the barium enema during large bowel investigation, no action required. Patient with beta-thalasemia. Incidental finding on abdominal ultrasound, no action required.
ITU, intensive treatment unit; U/S, ultrasound.
gin.10,12 The mechanical theory claims that air is absorbed into the mesenteric capillary veins through gastrointestinal mucosal barrier interruption or by increased intraluminal pressure. The infective theory of organism-derived gas is supported by the increased hydrogen concentration within the air cysts. Both theories represent separate pathways as proved by the absence of sepsis in some cases.10 A third theory explains the pulmonary origin, by air dissecting through the retroperitoneum, into the mesentery, and, finally, to the bowel subserosa and submucosa.8 The incidence of the concomitant occurrence of both signs varies in the literature. In our study, we reviewed the radiology department database for both terms over a period of 20 years since the implement of the CT scanner. Both signs occurred together in 41.7% of the cases; PVG occurred separately in 33.3% and PI occurred separately in 25% of the cases. Mohammed et al.12 described most cases of PVG to be associated with PI, whereas Nelson et al.10 mentioned 50% association. Many studies claimed that when accompanied by PVG, PI often is associated with bowel ischemia.4,12,14 Kung et al.15 added that the combination of pneumatosis intestinalis, portal venous gas, and acidosis typically portends bowel ischemia and inevitable necrosis. Furthermore, in cases with bowel ischemia, the presence of both signs together is highly suggestive of transmural bowel ischemia (91%) and is associated with higher mortality (72%), whereas each sign independently cannot differentiate between transmural and partial thickness bowel ischemia, and it was associated with lower mortality rates, 44% and 56% for PI and PVG, respectively.6 In our study, the incidence of bowel ischemia associated with the concomitant finding of both signs was 80% (4/5). This
figure could be affected by the small number of cases in this study as well as in other reviews. In fact, as both signs share the same etiologic origin, we support the opinion that the concomitant finding of portal venous gas should not be always regarded as an ominous sign as it does not necessarily suggest bowel ischemia. The different etiologies must be correlated clinically with the patient’s history.6,8 Since the late 1980s, the overall survival rate has increased. This is likely because of the increased incidence of iatrogenic cases and the enhanced detection by more sensitive diagnostic imaging modalities, eg, CT scan.12 Recent studies reported a decrease in the overall mortality from 75%, reported by Liebman et al. in 19784 down to 25% to 35%.7,16,17 Several imaging modalities were used in the diagnostic evaluation of patients with PVG. These include plain radiographic imaging of the abdomen, ultrasonography, Doppler ultrasonography, and CT. On a supine plain abdominal radiograph, PVG appears as branching, linear, radiolucent vessels that may extend from the region of the main portal vein toward the periphery of both hepatic lobes.18 However, substantial amounts of gas must be present for its detection at conventional radiography.19 Moreover, many authors consider ultrasonography and CT to be more sensitive tools in detection of PVG than conventional radiography.20 On real-time ultrasonography, PVG is viewed as small mobile echogenic foci moving quickly in the direction of blood flow inside the lumen of the portal vein. Doppler studies show these foci to produce audible crackles and sharp bidirectional spikes superimposed on the usual Doppler tracing of the portal vein.20 The main disadvantage of ultrasonography is that it is operator dependant; however, sev-
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
49
eral case reports described the detection of PVG on ultrasonography only and not on CT.20,21 At CT, PVG appears as tubular areas of decreased attenuation in the liver, predominantly in the left lobe. These low-attenuation areas are caused by the accumulation of gas in the intrahepatic portal veins, from where it is carried by centrifugal blood to the hepatic periphery.22 Intrahepatic PVG must be differentiated from air in the biliary tree (pneumobilia). In the latter condition, the air is located centrally (ie, it does not extend to within 2 cm of the liver capsule), and it tends to collect in the large bile ducts at the hilum because of the centripetal flow of bile.23 Pneumobilia also has a left lobe predilection at CT because of its more ventral location. In contrast, the collections of PVG are smaller and more numerous, and they are observed in the liver periphery.22 Finally, it is important to remember that PVG may appear and disappear rapidly, and it is possible that in many instances it is missed.24,25 By contrast, microvesicular gas collections, which are defined as 10-mm to 100-mm cysts or bubbles within the lamina propria, are associated predominantly with primary (benign) PI, whereas linear or curvilinear gas collections observed parallel to the bowel wall are found in secondary PI. Therefore, linear gas collections are usually an ominous sign.8 The duration of radiographically demonstrable PI varied from 1 to 21 days.7 The thickness of the wall of the small bowel is ordinarily 2-3 mm when the lumen is distended.26 Any segment of small bowel has a wall thickness greater than 4 mm is abnormal,26,27 and in the presence of PVG and/or PI may indicate ischemia. With regard to the management, most recent studies recommend correlating these findings with the history, clinical examination, and laboratory findings.5,11,12,14 Other studies classified the clinical management according to the etiology, whether iatrogenic or noniatrogenic.14,28 Fewer studies tried a schematic approach for the management, mainly classifying patients into 3 groups. Patients with established bowel ischemia on CT should have an immediate surgical intervention. Patients who are clinically stable should be treated conservatively. Finally, in equivocal cases, patients should have close monitoring or diagnostic laparoscopy.5,10,14 Both signs resolve spontaneously in any context due to the absorption of the gas in the circulation. The length of time depends mainly on the production of new gas and ranges from few minutes to 6 weeks.7,10 There is a lack of consensus about the prognostic value of both signs, as well as the relation between the degree of bowel ischemia and severity of either signs.5-7 In our study, the overall mortality was 41.7% (40% [2/5] and 42.9% [3/7] for cases with and without established bowel ischemia, respectively), p ⫽ 1. Despite the low number of cases, we do not support any prognostic index for either or both signs; the main prognostic criterion in the presence of these signs is the primary diagnosis. Similarly, the incidental finding of these signs in an asymptomatic patient does not seem to warrant any particular management scheme. The authors are aware that the reduced number of cases is a potential bias. This is either because of the rarity of the cases or the terms restrictions used in the computer search. 50
CONCLUSIONS PVG and PI should be considered as ominous radiologic signs only in patients with ominous surgical diagnoses. Despite an increase in the number of studies in the literature, they represent mostly case reports with few numbers. There is a need for a meta-analysis combining these case reports to look into the prognostic index of these signs and how they should affect the clinical management.
REFERENCES 1. Wolfe JN, Evans WA. Gas in the portal veins of the liver
in infants: a roentgenographic demonstration with postmortem anatomic correlation. Am J Roentgenol Radium Ther Med. 1955;74:486-488. 2. Susman N, Senturia HR. Gas embolization of the portal
venous system. Am J Roentgenol Radium Ther Nucl Med. 1960;83:847-850. 3. Lazar HP. Survival following portal venous air emboliza-
tion: report of a case. Am J Dig Dis. 1965;10:259-264. 4. Liebman PR, Patten MT, Manny J, et al. Hepatic-portal
venous gas in adults: etiology, pathophysiology and clinical significance. Ann Surg. 1978;187:281-287. 5. Hussain A, Mahmood H, El-Hasani S. Portal vein gas in
emergency surgery. World J Emerg Surg. 2008;3:21. 6. Wiesner W, Mortele KJ, Glickman NJ, Ji H, Ros PR.
Pneumatosis intestinalis and portomesentric venous gas in intestinal ischemia: correlation of CT findings with severity of ischemia and clinical outcome. AJR Roentgenol. 2001;177:1319-1323. 7. Knechtle SJ, Davidoff AM, Rice RP. Pneumatosis intesti-
nalis. Surgical management and clinical outcome. Ann Surg. 1990;212:160-165. 8. Goyal SK, Weltman DI, Balsam D. Pneumatosis Intesti-
nalis, 1955. E-medicine. Available at: http://emedicine. medscape.com/article/37. 9. Elliott C. Images in clinical medicine: pneumatosis intes-
tinalis and portal venous gas. N Engl J Med;2004:350:e3. 10. Nelson A, Millington TM, Sahani D, et al. Hepatic portal
venous gas, the ABCs of management. Arch Surg. 2009; 144:575-581. 11. Alqahtani S, Coffin C, Burak K, Chen F, MacGregor J,
Beck P. Hepatic portal venous gas: a report of two cases and a review of the epidemiology, pathogenesis, diagnosis and approach to management. Can J Gastroenterol. 2007; 21:309-313.
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
12. Mohammed A, Mohammed A, Khot U, Thomas D. Por-
20. Lafortune M, Trinh BC, Burns PN, et al. Air in the portal
tal venous gas— case report and review of literature. Anaethesia. 2007;(62):400-404.
vein: sonographic and Doppler manifestations. Radiology. 1991;180:667-670.
13. Abboud B, El Hachem J, Yazbeck T, Doumit C. Hepatic
21. Chevallier P, Peten E, Souci J, Chau Y, Padovani B, Bru-
portal venous gas: physiopathology, etiology, prognosis and treatment World J Gastroenterol. 2009;15:3585-3590. 14. Peloponissios N, Halkic N, Pugnale M, et al. Hepatic
portal gas in adults: review of the literature and presentation of a consecutive series of 11 cases. Arch Surg. 2003; 138:1367-1370. 15. Kung D, Ruan DT, Chan RK, Ericsson ML, Saund MS.
Pneumatosis intestinalis and portal venous gas without bowel ischemia in a patient treated with irinotecan and cisplatin. Dig Dis Sci. 2008;53:217-219. 16. Faberman RS, Mayo-Smith WW. Outcome of 17 pa-
tients with portal venous gas detected by CT. AJR Am J Roentgenol. 1997;169:1535-1538. 17. Iannitti DA, Gregg SC, Mayo-Smith WW, Tomolonis
RJ, Cioffi WG, Pricolo VE. Portal venous gas detected by computed tomography: is surgery imperative? Dig Surg. 2003;20:306-315. 18. Epelman M, Daneman A, Navarro OM, et al. Necrotizing
neton JN. Detection of portal venous gas on sonography, but not on CT. Eur Radiol. 2002;12:1175-1178. 22. Sebastià C, Quiroga S, Espin E, Boyé R, Alvarez-Castells
A, Armengol M. Portomesenteric vein gas: pathological mechanisms, CT findings, and prognosis. RadioGraphics. 2000;20:1213-1224. 23. Hou SK, Chern CH, How CK, Chen JD, Wang LM, Lee
CH. Hepatic portal venous gas: clinical significance of computed tomography findings. Am J Emerg Med. 2004; 22:214-218. 24. Lloyd DA, Cywes S. Intestinal stenosis and enterocyst
formation as late complications of neonatal necrotizing enterocolitis. J Pediatr Surg. 1973;8:479-486. 25. Vollman JH, Smith WL, Tsang RC. Necrotizing entero-
colitis with recurrent hepatic portal venous gas. J Pediatr. 1976;88:486-487. 26. Gore RM, Goldberg, HI. Computed tomographic evalu-
ation of the gastrointestinal tract in diseases other than primary adenocarcinoma. Radiol Clin North Am. 1982; 20:781-791.
enterocolitis: review of state-of-the-art imaging findings with pathological correlation. RadioGraphics. 2007;27: 285-305.
27. Ji H, Ros PR. Spiral CT of the small bowel. Appl Radiol-
19. Faberman RS, Mayo-Smith WW. Outcome of 17 pa-
28. Hong JJ, Gadaleta D, Rossi P, Esquivel J, Davis JM. Por-
tients with portal venous gas detected by CT. AJR Am J Roentgenol. 1997;169:1535-1538.
tal vein gas: a changing clinical entity. Arch Surg. 1997; 132:1071-1075.
ogy. 1999;28:11-15.
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
51
Portal Venous Gas and Pneumatosis Intestinalis; Radiologic Signs with Wide Range of Significance in Surgery Nader Naguib, MD, MRCS,* Peter Mekhail, MRCS,* Vivek Gupta, FRCS,* Nagy Naguib, MSc,† and Ashraf Masoud, FRCS* *Department of Surgery, Prince Charles Hospital, Merthyr Tydfil, United Kingdom, and †Department of Radiology, Johann Wolfgang Goethe University Hospital, Frankfurt, Federal Republic of Germany BACKGROUND: Portal vein gas (PVG) was described as an uncommon ominous radiologic sign usually harboring an intraabdominal catastrophe. When accompanied by pneumatosis intestinalis (PI), it is more predictive of bowel ischemia. Since the wide use of computed tomography (CT), both signs could also be viewed as incidental findings during routine radiologic investigations. METHODS: We present a series of 12 cases that showed either
or both signs, collected in a district general hospital between 1991 and 2011. RESULTS: The diagnoses in these cases varied between fatal bowel ischemia and the mere presence of radiologic signs in the absence of significant pathology. CONCLUSION: PVG and PI are radiologic signs that can
represent a wide range of pathology. (J Surg 69:47-51. © 2012 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.) KEY WORDS: portal venous gas, pneumatosis intestinalis
were reported, increasing the total number in literature to approximately 335 cases.5 In approximately 50% of the cases, PVG is associated with pneumatosis intestinalis (PI), gas within the bowel wall.6 Knechtle et al.7 described PI first in 1730 during postmortem dissection, more than 2 centuries earlier than the description of PVG and with a far greater number of cases in the literature (350 by 1990). PI has 2 forms: Primary PI is rather a benign condition with submucosal or subserosal cysts in the colon, and secondary PI with circumferential or linear air affecting any part of the gastrointestinal tract.8
METHODS The data were extracted from the computerized radiology database using the following search terms: “portal vein gas and/or air” and “pneumatosis intestinalis” between 1991 and 2011. The computed tomography (CT) service was introduced in the hospital in March 1991. Subsequent details on each case were obtained from clinical portals and theater database. A statistical analysis was performed using the Fisher exact test.
COMPETENCIES: Patient Care, Medical Knowledge, Practice
Based Learning and Improvement
RESULTS
INTRODUCTION
In 20 years, a total of 12 cases were identified (7 men and 5 women) with a median age of 66.5 years (range, 29-80 years). Six cases were identified by CT abdomen, 3 cases were identified on plain abdominal X-ray (AXR), 2 cases were identified incidentally on barium enema (BE), and 1 case was found incidentally on abdominal ultrasound examination. Both radiologic signs were present together in 5 cases (Fig. 1). PVG only was reported in 4 cases (Fig. 2), and PI only was reported in another 3 cases (Fig. 3). A breakdown of all cases is shown in Table 1. Six patients underwent laparotomy for an acute abdomen; 5 of them had both signs of PVG and PI on CT scan. Again,5 of these 6 patients had ischemic bowel and underwent resection of the ischemic segment. The sixth patient had a negative laparot-
Portal vein gas (PVG), which is the presence of air in the portal venous system, is a radiologic sign first described in 1955 by Wolfe and Evans1 in 6 neonates who died of bowel ischemia. The sign was described first in adults in 1960, by Susman and Senturia,2 but the first survivor with this sign was reported by Lazar in 1965.3 Liebman et al.,4 in 1978, reported mortality rate of 75% associated with this sign after collecting all 64 cases in the literature. Between 1975 and 2008, another 275 cases Correspondence: Inquiries to Nader Naguib, MD, MRCS, Department of Surgery, Prince Charles Hospital, Merthyr Tydfil, United Kingdom CF47 9DT; fax: ⫹⫹441-1685728126; e-mail: [email protected]
Journal of Surgical Education • © 2012 Association of Program Directors in Surgery Published by Elsevier Inc. All rights reserved.
1931-7204/$30.00 doi:10.1016/j.jsurg.2011.07.005
47
FIGURE 3. CT scan showing pneumatosis intestinalis.
FIGURE 1. CT scan showing portal venous gas and pneumatosis intestinalis.
omy with no surgical explanation offered for the patient’s symptoms and the associated PVG and PI. Four patients had incidental radiologic finding of PVG and/or PI; 2 found on a barium enema, 1 on an abdominal ultrasound, and 1 on AXR after a colonoscopy. Two patients were admitted to the hospital unwell and died shortly after. One had PVG and small bowel obstruction on AXR. The other had PI, and postmortem examination revealed drug overdose.
FIGURE 2. CT scan showing portal venous gas. 48
The overall mortality rate was 41.7% (5/12). Of the 7 patients who survived, 4 demonstrated PVG and/or PI while being investigated for a separate problem and were considered incidental findings (4/12). Only 3 patients survived among the remaining symptomatic 8 cases (not incidentally found), for a mortality rate of 62.5%.
DISCUSSION PVG and PI usually were described in the literature as separate entities, although both were described as ominous signs and were found to share the same etiologic factors and pathophysiologic mechanisms. It has been presumed that PI ascends from the draining venous mesentery and condenses in the portal venous system,9 so they should be considered as progressive steps in a single process.10 PVG is associated with PI when the intraluminal gas finds its way into the mesenteric veins, and if the gas does not reach the veins, then PI will be present alone. Occasionally, intraluminal gas may enter the portomesenteric veins directly without producing a radiologically detectable pneumatosis.6 Again, in the literature, the etiology for either signs was generally classified into (1) ischemic gastrointestinal disease, (2) nonischemic gastrointestinal disease, and (3) pulmonary disease.5,8 Bowel ischemia is the most common cause (61%) and carries a poor prognosis with associated mortality of 75% to 90%.4,5,6,10-12 In our study, the mortality rate associated with bowel ischemia was 40% (2/5). However, noncritical causes can lead to these signs; ie, the finding of PVG and/or PI may just be an incidental finding and does not warrant surgical intervention. These causes include diagnostic gastrointestinal procedures (eg, endoscopy and barium enema), trauma, chemotherapy, immune suppressants after transplantation, and idiopathic causes.5,7,13 The iatrogenic and idiopathic causes for PVG were reported as 3% and 1.8%, respectively.5 The 2 main hypotheses explaining the occurrence of these radiologic signs are the mechanical- and bacterial-derived ori-
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
TABLE 1. Clinical Breakdown of the Cases PVG
PI
Age
Sex
1
Yes
Yes
80
F
2
Yes
Yes
74
3
Yes
Yes
4
Yes
5
Radiology
Survived
Diagnosis
CT
Yes
M
CT
Yes
67
M
CT
Yes
Yes
66
F
CT
No
Yes
Yes
71
M
CT
No
6 7 8
Yes No No
No Yes Yes
65 68 29
M M F
CT AXR AXR
No Yes No
9
Yes
No
64
M
AXR
No
10
Yes
No
63
F
BE
Yes
11
No
Yes
72
F
BE
Yes
12
Yes
No
32
M
U/S
Yes
Afferent loop ischemia after partial gastrectomy and Roux en Y anastmosis. Refashioning of the anastmosis was performed Ileal loop ischemia. Patient had resection and exteriorization of both ends. Small bowel obstruction and bowel necrosis. Laparotomy; resection and primary anastomosis Acute surgical abdomen, bowel necrosis. Laparotomy; resection and primary anastomosis Abdominal pain on day 6 postgastrectomy; increased lactate. Negative laparotomy. Small bowel obstruction, bowel necrosis on laparotomy. Incidental finding after a colonoscopy, no action required. Died in ITU same day, postmortem showed drug overdose and pulmonary oedema. Rectal cancer, Small bowel obstruction, died shortly after admission. Incidental finding at the barium enema during large bowel investigation, no action required. Incidental finding at the barium enema during large bowel investigation, no action required. Patient with beta-thalasemia. Incidental finding on abdominal ultrasound, no action required.
ITU, intensive treatment unit; U/S, ultrasound.
gin.10,12 The mechanical theory claims that air is absorbed into the mesenteric capillary veins through gastrointestinal mucosal barrier interruption or by increased intraluminal pressure. The infective theory of organism-derived gas is supported by the increased hydrogen concentration within the air cysts. Both theories represent separate pathways as proved by the absence of sepsis in some cases.10 A third theory explains the pulmonary origin, by air dissecting through the retroperitoneum, into the mesentery, and, finally, to the bowel subserosa and submucosa.8 The incidence of the concomitant occurrence of both signs varies in the literature. In our study, we reviewed the radiology department database for both terms over a period of 20 years since the implement of the CT scanner. Both signs occurred together in 41.7% of the cases; PVG occurred separately in 33.3% and PI occurred separately in 25% of the cases. Mohammed et al.12 described most cases of PVG to be associated with PI, whereas Nelson et al.10 mentioned 50% association. Many studies claimed that when accompanied by PVG, PI often is associated with bowel ischemia.4,12,14 Kung et al.15 added that the combination of pneumatosis intestinalis, portal venous gas, and acidosis typically portends bowel ischemia and inevitable necrosis. Furthermore, in cases with bowel ischemia, the presence of both signs together is highly suggestive of transmural bowel ischemia (91%) and is associated with higher mortality (72%), whereas each sign independently cannot differentiate between transmural and partial thickness bowel ischemia, and it was associated with lower mortality rates, 44% and 56% for PI and PVG, respectively.6 In our study, the incidence of bowel ischemia associated with the concomitant finding of both signs was 80% (4/5). This
figure could be affected by the small number of cases in this study as well as in other reviews. In fact, as both signs share the same etiologic origin, we support the opinion that the concomitant finding of portal venous gas should not be always regarded as an ominous sign as it does not necessarily suggest bowel ischemia. The different etiologies must be correlated clinically with the patient’s history.6,8 Since the late 1980s, the overall survival rate has increased. This is likely because of the increased incidence of iatrogenic cases and the enhanced detection by more sensitive diagnostic imaging modalities, eg, CT scan.12 Recent studies reported a decrease in the overall mortality from 75%, reported by Liebman et al. in 19784 down to 25% to 35%.7,16,17 Several imaging modalities were used in the diagnostic evaluation of patients with PVG. These include plain radiographic imaging of the abdomen, ultrasonography, Doppler ultrasonography, and CT. On a supine plain abdominal radiograph, PVG appears as branching, linear, radiolucent vessels that may extend from the region of the main portal vein toward the periphery of both hepatic lobes.18 However, substantial amounts of gas must be present for its detection at conventional radiography.19 Moreover, many authors consider ultrasonography and CT to be more sensitive tools in detection of PVG than conventional radiography.20 On real-time ultrasonography, PVG is viewed as small mobile echogenic foci moving quickly in the direction of blood flow inside the lumen of the portal vein. Doppler studies show these foci to produce audible crackles and sharp bidirectional spikes superimposed on the usual Doppler tracing of the portal vein.20 The main disadvantage of ultrasonography is that it is operator dependant; however, sev-
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
49
eral case reports described the detection of PVG on ultrasonography only and not on CT.20,21 At CT, PVG appears as tubular areas of decreased attenuation in the liver, predominantly in the left lobe. These low-attenuation areas are caused by the accumulation of gas in the intrahepatic portal veins, from where it is carried by centrifugal blood to the hepatic periphery.22 Intrahepatic PVG must be differentiated from air in the biliary tree (pneumobilia). In the latter condition, the air is located centrally (ie, it does not extend to within 2 cm of the liver capsule), and it tends to collect in the large bile ducts at the hilum because of the centripetal flow of bile.23 Pneumobilia also has a left lobe predilection at CT because of its more ventral location. In contrast, the collections of PVG are smaller and more numerous, and they are observed in the liver periphery.22 Finally, it is important to remember that PVG may appear and disappear rapidly, and it is possible that in many instances it is missed.24,25 By contrast, microvesicular gas collections, which are defined as 10-mm to 100-mm cysts or bubbles within the lamina propria, are associated predominantly with primary (benign) PI, whereas linear or curvilinear gas collections observed parallel to the bowel wall are found in secondary PI. Therefore, linear gas collections are usually an ominous sign.8 The duration of radiographically demonstrable PI varied from 1 to 21 days.7 The thickness of the wall of the small bowel is ordinarily 2-3 mm when the lumen is distended.26 Any segment of small bowel has a wall thickness greater than 4 mm is abnormal,26,27 and in the presence of PVG and/or PI may indicate ischemia. With regard to the management, most recent studies recommend correlating these findings with the history, clinical examination, and laboratory findings.5,11,12,14 Other studies classified the clinical management according to the etiology, whether iatrogenic or noniatrogenic.14,28 Fewer studies tried a schematic approach for the management, mainly classifying patients into 3 groups. Patients with established bowel ischemia on CT should have an immediate surgical intervention. Patients who are clinically stable should be treated conservatively. Finally, in equivocal cases, patients should have close monitoring or diagnostic laparoscopy.5,10,14 Both signs resolve spontaneously in any context due to the absorption of the gas in the circulation. The length of time depends mainly on the production of new gas and ranges from few minutes to 6 weeks.7,10 There is a lack of consensus about the prognostic value of both signs, as well as the relation between the degree of bowel ischemia and severity of either signs.5-7 In our study, the overall mortality was 41.7% (40% [2/5] and 42.9% [3/7] for cases with and without established bowel ischemia, respectively), p ⫽ 1. Despite the low number of cases, we do not support any prognostic index for either or both signs; the main prognostic criterion in the presence of these signs is the primary diagnosis. Similarly, the incidental finding of these signs in an asymptomatic patient does not seem to warrant any particular management scheme. The authors are aware that the reduced number of cases is a potential bias. This is either because of the rarity of the cases or the terms restrictions used in the computer search. 50
CONCLUSIONS PVG and PI should be considered as ominous radiologic signs only in patients with ominous surgical diagnoses. Despite an increase in the number of studies in the literature, they represent mostly case reports with few numbers. There is a need for a meta-analysis combining these case reports to look into the prognostic index of these signs and how they should affect the clinical management.
REFERENCES 1. Wolfe JN, Evans WA. Gas in the portal veins of the liver
in infants: a roentgenographic demonstration with postmortem anatomic correlation. Am J Roentgenol Radium Ther Med. 1955;74:486-488. 2. Susman N, Senturia HR. Gas embolization of the portal
venous system. Am J Roentgenol Radium Ther Nucl Med. 1960;83:847-850. 3. Lazar HP. Survival following portal venous air emboliza-
tion: report of a case. Am J Dig Dis. 1965;10:259-264. 4. Liebman PR, Patten MT, Manny J, et al. Hepatic-portal
venous gas in adults: etiology, pathophysiology and clinical significance. Ann Surg. 1978;187:281-287. 5. Hussain A, Mahmood H, El-Hasani S. Portal vein gas in
emergency surgery. World J Emerg Surg. 2008;3:21. 6. Wiesner W, Mortele KJ, Glickman NJ, Ji H, Ros PR.
Pneumatosis intestinalis and portomesentric venous gas in intestinal ischemia: correlation of CT findings with severity of ischemia and clinical outcome. AJR Roentgenol. 2001;177:1319-1323. 7. Knechtle SJ, Davidoff AM, Rice RP. Pneumatosis intesti-
nalis. Surgical management and clinical outcome. Ann Surg. 1990;212:160-165. 8. Goyal SK, Weltman DI, Balsam D. Pneumatosis Intesti-
nalis, 1955. E-medicine. Available at: http://emedicine. medscape.com/article/37. 9. Elliott C. Images in clinical medicine: pneumatosis intes-
tinalis and portal venous gas. N Engl J Med;2004:350:e3. 10. Nelson A, Millington TM, Sahani D, et al. Hepatic portal
venous gas, the ABCs of management. Arch Surg. 2009; 144:575-581. 11. Alqahtani S, Coffin C, Burak K, Chen F, MacGregor J,
Beck P. Hepatic portal venous gas: a report of two cases and a review of the epidemiology, pathogenesis, diagnosis and approach to management. Can J Gastroenterol. 2007; 21:309-313.
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
12. Mohammed A, Mohammed A, Khot U, Thomas D. Por-
20. Lafortune M, Trinh BC, Burns PN, et al. Air in the portal
tal venous gas— case report and review of literature. Anaethesia. 2007;(62):400-404.
vein: sonographic and Doppler manifestations. Radiology. 1991;180:667-670.
13. Abboud B, El Hachem J, Yazbeck T, Doumit C. Hepatic
21. Chevallier P, Peten E, Souci J, Chau Y, Padovani B, Bru-
portal venous gas: physiopathology, etiology, prognosis and treatment World J Gastroenterol. 2009;15:3585-3590. 14. Peloponissios N, Halkic N, Pugnale M, et al. Hepatic
portal gas in adults: review of the literature and presentation of a consecutive series of 11 cases. Arch Surg. 2003; 138:1367-1370. 15. Kung D, Ruan DT, Chan RK, Ericsson ML, Saund MS.
Pneumatosis intestinalis and portal venous gas without bowel ischemia in a patient treated with irinotecan and cisplatin. Dig Dis Sci. 2008;53:217-219. 16. Faberman RS, Mayo-Smith WW. Outcome of 17 pa-
tients with portal venous gas detected by CT. AJR Am J Roentgenol. 1997;169:1535-1538. 17. Iannitti DA, Gregg SC, Mayo-Smith WW, Tomolonis
RJ, Cioffi WG, Pricolo VE. Portal venous gas detected by computed tomography: is surgery imperative? Dig Surg. 2003;20:306-315. 18. Epelman M, Daneman A, Navarro OM, et al. Necrotizing
neton JN. Detection of portal venous gas on sonography, but not on CT. Eur Radiol. 2002;12:1175-1178. 22. Sebastià C, Quiroga S, Espin E, Boyé R, Alvarez-Castells
A, Armengol M. Portomesenteric vein gas: pathological mechanisms, CT findings, and prognosis. RadioGraphics. 2000;20:1213-1224. 23. Hou SK, Chern CH, How CK, Chen JD, Wang LM, Lee
CH. Hepatic portal venous gas: clinical significance of computed tomography findings. Am J Emerg Med. 2004; 22:214-218. 24. Lloyd DA, Cywes S. Intestinal stenosis and enterocyst
formation as late complications of neonatal necrotizing enterocolitis. J Pediatr Surg. 1973;8:479-486. 25. Vollman JH, Smith WL, Tsang RC. Necrotizing entero-
colitis with recurrent hepatic portal venous gas. J Pediatr. 1976;88:486-487. 26. Gore RM, Goldberg, HI. Computed tomographic evalu-
ation of the gastrointestinal tract in diseases other than primary adenocarcinoma. Radiol Clin North Am. 1982; 20:781-791.
enterocolitis: review of state-of-the-art imaging findings with pathological correlation. RadioGraphics. 2007;27: 285-305.
27. Ji H, Ros PR. Spiral CT of the small bowel. Appl Radiol-
19. Faberman RS, Mayo-Smith WW. Outcome of 17 pa-
28. Hong JJ, Gadaleta D, Rossi P, Esquivel J, Davis JM. Por-
tients with portal venous gas detected by CT. AJR Am J Roentgenol. 1997;169:1535-1538.
tal vein gas: a changing clinical entity. Arch Surg. 1997; 132:1071-1075.
ogy. 1999;28:11-15.
Journal of Surgical Education • Volume 69/Number 1 • January/February 2012
51