Another look at pneumoperitoneum

Another Benjamin

Look

at Pneumoperitoneum

Felson, M.D., and Jerome F. Wiot. M.D.

T

HE RADIOLOGIST can and does speak with authority about pneumoperitoneum. It is one of the first things we look for on abdominal films, and we see it often. We know how often we fail to find it in perforated peptic ulcer (3379 and the smallest amount that we can detect (1 cc). 25,2* We are aware that there is more of it with cecat than with duodenal perforation, and little or none of it with perforated appendix or colon diverticulum. But there still are situations that stump us. This presentation deals with two of them-postoperative and asymptomatic pneumoperitoneum. POSTOPERATIVE

PNEUMOPERITONEUM

Residual peritoneal air is a common finding after laparotomy. How then does one detect gastrointestinal perforation or anastomotic disruption in the recently operated patient who complains of abdominal pain? To answer this question, we have to ask several other ones: How often is gas trapped in the peritoneal sac after an uncomplicated operation, and how long does it remain there? VariHarrison, Litwer, and Gerwig noted ous answers are cited in the literature. 8,32*37 a higher incidence of postoperative pneumoperitoneum among asthenie individuals and in those who had upper abdominal operations.” They also stated that the duration of the pneumoperitoneum was proportional to the original volume of gas left in the peritoneum and was not related to distension of the intestinal lumen, postoperative infection, or other factors. Svartholm and Zwetnow, studying children from 4-16 yr of age, observed that younger children absorbed air at a faster rate than older ones. 35 Two-hundred consecutive patients who underwent laparotomy at the Cincinnat.i General Hospital were studied by Bryant, Wiot, and Kloecker.” An upright or decubitus film was taken on the day of operation and every day or two thereafter until all the gas disappeared. Pneumoperitoneum was demonstrated in 58%. In some, roentgenograms were taken at 5-, lo-, and 20-min intervals after the patient was placed in either the upright or decubitus position. There was a definite increase in the amount of free gas between the 5- and lo-min films but not thereafter. When both upright and decubitus projections were obtained, the amount of gas generally appeared larger on the upright film. Absorption of the pneumoperitoneum required from 1-24 days and appeared to relate only to the volume originally trapped, as determined from the first film. Larger amounts of gas were found after upper abdominal and pelvic operations; none at all remained after appendectomy (eight patients) or vaginal hysterectomy (three patients). The use of drains did not seem to affect the quantity of gas except for one patient in whom an increasing amount accumulated. Benjamin Felson, M.D.: Professor of Radiology and Direcior. Department of Radiology, IJniversity of Cincinnati College of Medicine, Cincinnati, Ohio. Jerome F. Wiot, M.D.: Professor of Radiology and Direcior, Department of Radiology, Cincinnati General Hospital, Cincinnati, Ohio 45229. o 1,973 by Grune & Srratron, Inc. Seminars in Roentgenology, Vol. VIII. No. 4 (October).

1973

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presumably entering through a drain. Neither the kind of incision nor the nature of the anesthesia appeared to be related to the presence or amount of pneumoperitoneum. Surprisingly, peritonitis seemed to have no influence on the presence or rate of absorption of the gas. The body habitus of the patient, however, appeared to play a major role in the incidence and amount of postoperative air. More than 80% of the asthenic patients, but only 252, of the obese ones, showed pneumoperitoneum. The thin patients also had a larger amount of gas, and consequently it persisted longer. In the obese patients, the gas nearly always disappeared by the third postoperative day. Wiot, Benton, and McAlister performed a similar study on 100 infants and 30% showed free air on the first postoperative day. children. 39Approximately It was still present in the four patients on the fourth day. At 6 days, gas was still seen in two, and in one of them, it remained for 38 days. Almost all the findings in the first study were corroborated. It was concluded that children and obese adults trap less air initially and therefore retain it for only a brief time. The same authors injected turpentine intraperitoneally in mice to produce mild peritonitis and then induced pneumoperitoneum. The absorption rate of the gas and the time required for its complete disappearance were no different from the control group of mice, which received pneumoperitoneum alone. To sum up, the roentgen demonstration of free gas should not enter into decisions of diagnosis or management of postoperative symptoms, although pneumoperitoneum in obese patients and children more than 3 days after operation should be considered with suspicion. Increase in the amount of gas has significance only if the films have been made with the patient in similar position for the same length of time, and in the absence of abdominal drains. SPONTANEOUS

PNEUMOPERITONEUM

WITHOUT

PERITONITIS

Pneumoperitoneum in the unoperated patient generally indicates a perforated hollow viscus and hence is a surgical emergency. However, occasional instances of free peritoneal gas without gastrointestinal perforation have been reported. Although the patients are only mildly ill or even totally asymptomatic, many have been subjected to immediate laparotomy with puzzling results: no perforation, no peritonitis, and often no explanation for the presence of the peritoneal gas. This condition has been called idiopathic pneumoperitoneum, 4 but since the cause for some of the cases is known or suspected, we prefer the term spontaneous pneumoperitoneum without peritonitis. Only 30 cases were found in a review of the literature up to 1968. In that year, ten additional cases were reported from the University of Cincinnati Medical Center.’ We found three more patients reported in the past 5 yr. Of these 43 patients, two were infants, 11 were in their 20s six in their 30s or 40s and 24 were over 50. The oldest patient was 81. The sex distribution was about even, but all 11 of those in the third decade were women, a fact that may have some bearing on the etiology in this age group, as will be discussed later. As the time the pneumoperitoneum was discovered, acute abdominal symptoms were present in 30 patients, absent in eight, and unstated in five. Most of the symptomatic patients were not very sick, although a few were severely ill.

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1. Conditions

Associated

with

Spontaneous

Pneumoperitoneum

Without

Peritonitis

No of Patents’ Peptic ulcer Pulmonary tuberculosrs Pneumatosis cystoides

intestinalis

Postpartum Postoperatrve Jejunal diverticulosis Lobar pneumoma

3 4 4 2

Pneumomediastinum Pulmonary-peritoneal fistula Carcinoma of stomach, regronal enteritis,

2 2

megacolon with voIvuIus. Ancylostoma infestation, carcmoma of lung, pulmonary emphysema, ulcerative colitrs Other (heart disease, stroke, uropathy. etc.) None ‘Some

7 5 4

1 each 7 8

(patients had more than one

In the eight patients without acute symptoms, the free peritoneal air was usually discovered accidentally on films taken for other reasons. Of the 43 patients, 35 had at least one associated condition, recent or current (Table 1). The diagnosis of pneumoperitoneum without peritonitis was confirmed by operation or autopsy in 25 patients. On opening the peritoneum, there was a gush of gas, generally odorless, but with a fecal odor in a few. The gross appearance of the peritoneum and viscera was entirely normal in 15 of the 25. The ten remaining verified cases showed a variety of gastrointestinal lesions. including peptic ulcer, pneumatosis cystoides intestinalis, jejunal diverticulosis. or the like (Table 1). Analysis of the peritoneal gas in three patients indicated the following: nitrogen 76Y-94x, carbon dioxide 3.6%-6.4x, and oxygen 2.5”;.---5.82,. A small amount of methane was found in two patients. In ten of the 18 unoperated patients, follow-up examinations were recorded. The pneumoperitoneum disappeared in less than 11 days in four, but persisted from 2 wk to many months in six. Four of our own patients were in the persistent group, the peritoneal gas remaining for 2 wk, 5 wk, 2 mo, and 8 mo. At least 11 of the total group of 43 patients had recurrent episodes of pneumoperitoneum.

Etiology Many theories have been advanced to explain spontaneous pneumoperitoneum without peritonitis. We believe that a number of mechanisms are involved, each accounting for some cases. Female genital tract. In women, air may enter the peritoneal cavity via the genital tract, as in the Rubin test. In several of the reported cases, the A case has also been repneumoperitoneum followed a vaginal douche. 26~34,38 corded in which the air entered via a vaginal-tubal fistula 1 yr after vaginal hysterectomy. 36The sound of gas bubbling up into the abdomen can sometimes be heard during pelvic examination, according to some gynecologists but, as

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with statements concerning spontaneous pneumoperitoneum in female water skiers, the evidence is to our knowledge undocumented phonographically or roentgenographically. It has even been conjectured that cough and dyspnea, causing sudden alteration in intraperitoneal pressure, promote uterotubal entry of air. Position may also play a role. Spontaneous pneumoperitoneum in the postpartum period (three patients), a time when douches and knee-chest exercises are common, favors this view. 5*‘3,23.24 One of our patients, a 77-yr-old woman, was found unconscious from a stroke at home, her head on the floor and her body in bed. An upright film of the abdomen, taken because of marked distension, showed a large amount of free peritoneal gas. At operation and at autopsy, no evidence of intestinal perforation or peritonitis was found. It was surmised that the air had been “aspirated” through the uterus and tubes as a result of position. The fact that all 1I patients in their 20s were women also lends support to the theory of genital entry. The amount of pneumoperitoneum in these young women was generally much smaller than in the rest of the patients. In four of the five young women operated on because of pneumoperitoneum, no associated disease was found. Perhaps the best evidence favoring this portal of entry of gas is that afforded by case reports of two women, each of whom had five bouts of pneumoperitoneum. ‘8*4’Application of a well-fitted cervical diaphragm in one, and bilateral salpingectomy in the other prevented further recurrence. Gastrointestinal tract. Pneumoperitoneum may occur as a complication of pneumatosis cystoides intestinalis. 9 In one unoperated patient, typical pneumatosis cysts were visible in the colon wall on barium enema. The pneumoperitoneum persisted for I mo. Since intramural intestinal gas is readily overlooked roentgenographically and even surgically, it is reasonable to suspect that other casesof unexplained chronic pneumoperitoneum are the result of rupture of a gas cyst. In four other patients in our series, the pneumoperitoneum was shown at operation to arise from localized bubbling of intestinal gas through the wall of a jejunal diverticulum.2~3~‘2*20.27 Th e intestinal wall appeared intact at the site of leakage, with no evidence of acute inflammation. Spontaneous pneumoperitoneum without peritonitis may be the result of a forme fruste perforation of a peptic ulcer. It has been postulated that a tiny perforation, easily missed at operation, may produce a valve-like flap that permits only gas to escape from the lumen. This kind of valve formation has Others believe that natural peritoneal immunity actually been observed. 29133 may prevent a small perforation from producing peritonitis. The high incidence of peptic ulcer in the entire series (seven of 43 cases) suggests that subclinical perforation may at times be responsible for the pneumoperitoneum. A similar leakage may result from lesions other than peptic ulcer, such as cancer of the stomach and regional enteritis. Can gas leak through the thinned-out wall of a distended segment of gut? Theoretically, a minute diastasis resulting from stretching of the tissues could break the airtight seal of the gastric or intestinal wall, permitting egress of gas. This might explain some of the cases of pneumoperitoneum associated with marked distension of the stomach as, for example, in aerophagy.** Several reported cases of pneumoperitoneum complicating gastroscopy also fall into Operation failed to disclose gastric perforation or other this category. 6~17v3’

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441

lesion or evidence of peritonitis. As part of the gastroscopy procedure the stomach is pumped up. Leakage of gas through the apparently intact wall of the distended viscus has actually been demonstrated at the operating table in this situation. Additional convincing evidence that gas can traverse the intact wall of a distended stomach is afforded by the report of a patient in whom pneumoperitoneum developed after a heavy meal followed by a dose of sodium bicarbonate. At operation, gas was seen bubbling through the intact wall of the greatly distended stomach. 29Another example was a case recently shown to us by Dr. Richard B. Mulvey. A victim of near drowning, the patient had developed pneumoperitoneum after mouth-to-mouth resuscitation, presumably performed cover-passionately! The stomach appeared moderately distended by gas. The peritoneal air was quickly absorbed. Danis et al. recorded intramural intestinal gas and portal vein gas in a child with mucoviscidosis who had received a hydrogen peroxide enema to loosen hardened stool. I5 He was able to reproduce the roentgen findings in dogs by administering a hydrogen peroxide enema. We confirmed this experiment and also, by injecting hydrogen peroxide into a loop of human intestine removed at autopsy, demonstrated passage of gas bubbles through the intact gut wall. There is ample evidence, then, that the gastrointestinal tract is not always “gas tight.” Respiratory tract. The high rate of thoracic disease in the collected series (at least I I cases) suggests a causal relationship to the pneumoperitoneum. Gas from a pneumomediastinum may dissect downward into the extraperitoneal tissues and then rupture into the peritoneal sac. “,40 We recently saw an example of this that followed tracheal injury during anesthesia. The statistical relationship between pneumatosis cystoides intestinalis and pulmonary disease’* suggests a more indirect mechanism. Reports by Britt et al.” and McGlone et al.2” bring up still another possible route: a pulmonary-peritoneal fistula. We believe that each of the mechanisms described above accounts for some of the cases of pneumoperitoneum without peritonitis. In young women, the genital system appears to be the most common site of entry. Intraperitoneal rupture of an intestinal gas cyst is another cause; so is peptic ulcer. Leakage of gas through the intact wall of a distended stomach or intestine is probably a fairly common source, and extension from the lung an occasional one. It is important that the clinician and the roentgenologist realize that pneumoperitoneum does not invariably mean gastrointestinal perforation and therefore does not always require operation. Spontaneous pneumoperitoneum without peritonitis can be recognized by the trivial or absent clinical and laboratory signs of an acute abdominal condition. Obviously, patients on steroid therapy and those in whom the level of consciousness is impaired may have frank perforation of the gut with few complaints, so prudent judgment and meticulous observation are always required. ACKNOWLEDGMENT Drs. .John E. Albers and William A. Altemeier supplied much of the impetus for the study on spontaneous pneumoperitoneum. We are grateful to Drs. Armand Brodeur, Richard B. Mulveq. and Warner A. Peck for affording us the opportunity to review the films on their patients. James T. Eastman, George E. Pittinos, Robert J. Smyth. and Peter W. Wagner, medical students. helped with the literature review.

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REFERENCES I. Albers JE, Altemeier WA, Felson B: Spontaneous pneumoperitoneum without acute peritonitis, unpublished 2. Altemeier WA, Bryant LR, Wulsin JH: The surgical significance of jejunal diverticulosis. Arch Surg 86:732-744, 1963 3. Armitage HV: Pneumoperitoneum associated with jejunal diverticulosis. Pa Med 73: 61-62, 1970 4. Ayres RW, Beeson CR, Scruggs JB Jr: Idiopathic pneumoperitoneum: a review of the literature and report of a case. Am J Dig Dis 17:345-347, 1950 5. Bean LL, Garrett RI: Spontaneous pneumoperitoneum (from exercise during puerperium). US Armed Forces Med J 5:375, 1954 6. Berk JE: Pneumoperitoneum following gastroscopy without evidence of perforation at laparotomy fourteen hours later. Gastroenterology 6:218, 1946 7. Bevan PG: Incidence of post-operative pneumoperitoneum and its significance. Br Med J 2:6055609, 196 I 8. Bevan PG: Post-operative pneumoperitoneum and pulmonary collapse. Br Med J 2:609-613, 1961 9. Bilger M: Pneumatosis cystoides intestinalis in children: report of a case complicated with fatal pneumoperitoneum. J Pediatr 49: 445-449, 1956 IO. Britt CI, Christoforidis AJ, Andrew NC: pneumoperiAsymptomatic spontaneous toneum. Am J Surg 101:232-235, 1961 1 I. Bryant LR, Wiot JF, Kloecker RJ: A study of the factors affecting the incidence and duration of postoperative pneumoperitoneum. Surg Gynecol Obstet 117:1455150, 1963 12. Bryk D: Unusual causes of small-bowel pneumatosis: perforated duodenal ulcer and perforated jejunal diverticula. Radiology 106: 299-302, 1973 13. Conn HQ, La Fon WF: Recurrent spontaneous pneumoperitoneum. Am J Obstet Gynecol7 I : 1342- 1347, 1956 14. Conole FD, D’Angelo AA: Resection of pharyngeal diverticulum with spontaneous development of tension pneumoperitoneum. Am J Surg 83:580-583, 1952 15. Danis RK, Brodeur AE, Shields J: The danger of hydrogen peroxide as a colonic irrigating solution. J Pediatr Surg 2: 13 I-133, 1967 16. Felson B: Abdominal gas: a roentgen approach. Ann NY Acad Sci 150:141~161, 1968 17. Fierst SM, Robinson HM, Lasagna L:

Interstitial gastric emphysema following gastroscopy; its relation to the syndrome of pneumoperitoneum and generalized emphysema with no evident perforation. Ann Intern Med 34:120221212, 1951 18. Fredrikson H: A case of pneumoperitoneum. Acta Obstet Gynecol Stand 34:568, 1956 19. Harrison I, Litwer H, Gerwig WH Jr: Studies on the incidence and the duration of postoperative pneumoperitoneum. Ann Surg 145:59l-594, 1957 20. Herrington JL Jr: Perforation of acquired diverticula of the jejunum and ileum. Surgery 51:426-433, 1962 21. Herrington JL Jr: Spontaneous asymptomatic pneumoperitoneum: a complication of jejunal diverticulosis. Am J Surg ll3:567-570, 1967 22. Keyting WS, McCarver RR, Kovarik JL, et al: Pneumatosis intestinalis: a new concept. Radiology 76:733-741, 1961 23. Lozman H, Newman AJ: Spontaneous pneumoperitoneum occurring during postpartum exercises in the knee-chest position. Am J Obstet Gynecol 72:903-905, 1956 24. McGlone FB, Vivion CG Jr, Meir L: Spontaneous pneumoperitoneum. Gastroenterology 5 I :393-398, 1966 25. Miller RE: The technical approach to the acute abdomen. Semin Roentgen01 8:2677279, 1973 26. Moberg G: Two cases of pneumoperitoneum without any signs of perforation of alimentary canal or abdominal wall. Acta Radio1 18:798-806, 1937 27. Nanson EM, Dragan GE: A spontaneous pneumoperitoneum due to jejunal diverticulosis. Ann Surg 143:112-l 16, 1956 28. Nelson SW, Christoforidis AJ, Roenigk WJ: Barium suspensions vs. water-soluble iodine compounds in the study of obstruction of the small bowel: an experimental study of physiologic characteristics and radiographic value. Radiology 80:252-254, 1963 29. Norpoth H: Beitrag zur Frlge des spontanen Pneumoperitoneums. Zbl Chir 75: 450-455, 1950 30. -Papp JP, Sullivan BH Jr: Spontaneous pneumoperitoneum without peritonitis: report of a case. Cleve Clin Quart 32: l49- 154, I965 31. Schiff L, Stevens RJ, Goodman S: Pneumoperitoneum following use of the flexible gastroscope. Ann Intern Med 14: 1283-1287, 1941

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32. Sergievskiy SA: Post-operative pneumoperitoneum and its influence on the development of pulmonary complications. Vestn Khir 67:23, 1947 33. Singer HA: Valvular pneumoperitoneum. JAMA 99:2171-2180, 1932 34. Ste’istrljm B: Discussion of etiology of spontaneous pneumoperitoneum found during roentgen examination. Acta Radio1 18:625, 1937 35. Svartholm F. Zwetnow N: Resorption of postoperative pneumoperitoneum in children. Acta Radio1 (Diagn) 8:514-518, 1969 36. Tabrisky J, Mallin LP, Smith JA 3d: Pneumoperrtoneum after coitus. A complication due to uterine tube prolapse after

vagtnal hysterectomy. 220, 1972

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40:2 I8

37. von Keiser D, LemmertL K: uber dte dauer des postoperativen pneumoperitonrums Chirurg 18:260, 1947 38. Walker MA: Pneumoperitoneum folloxing a douche. J Kans Med Sot 43:55. 1942 39. Wiot JF, Benton C. McAlister WH: Postoperative pneumoperitoneum m children. Radiology 89:285-288. 1967 40. Wolf HG: Beitrlge zur Diagnose und Atiologte des spontanen Pneumoperitoneums beim Neugebornen. Radio1 Clin 27:193. 1958 41. Wrtght AR: Spontaneous pneumoperrtoneum. AMA Arch Surg 78:500 502. 1959