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Scintillation scanning in the diagnosis of hepatic abscess in children
August, 1970 T h e Journal of P E D I A T R I C S
211
Scintillation scanning in the diagnosis of hepatic abscess in children Liver scintiscanning has been widely used in adults [or the diagnosis and localization of intrahepatic lesions. The use of this modality in children with liver abscess is discussed and illustrated.
Robert E. O'Mara, M.D., and John G. McAfee, M.D. SYRAGUStg~
N.
Y.
o f liver abscess is f r e difficult in children. The complaints are often nonspecific and the diagnosis usually reached by exclusion after considerable delay. There may be no history of a predisposing event such as trauma. Fever (often listed as of unknown origin), leukocytosis, abdominal discomfort or pain, sometimes localized to the right upper quadrant, and irritability comprise the most common presenting findings. Although hepatic radioisotopic imaging is widely used in adults for the diagnosis of focal hepatic lesions, it has seldom been mentioned in the pediatric literature. Two brief case histories are therefore presented as an illustration of how the hepatic scintiscan may pinpoint the diagnosis of hepatic abscess. In addition, a technique of hepatic imaging for children is described briefly. T g ~
DI A G N O S I S
quently
MATERIALS AND METHODS Technetium-99m sulfur colloid was selected as the agent of choice for hepatic imaging. From the Division o[ Nuclear Medicine, Department of Radiology, Upstate Medical Center, State University of New York.
This is easily prepared in the laboratory 1 and is also commercially available in kit form (Tesuloid Kit, Squibb Division of Nuclear Medicine, New Brunswick, N. J.). A dose of 1 to 3 millicuries, depending on the child's age and weight, was administered intravenously. The scans were obtained on a scanner with two opposing 5 inch crystal detectors, permitting two projections to be obtained simultaneously. Average scanning time is about 30 minutes for anterior, posterior, and both lateral projections. When a child is seriously ill, restless, or uncooperative, rectilinear scanning is not satisfactory because of motion artifacts. In this situation, scintiphotos may be obtained more quickly and easily with an Anger camera obtaining 300,000 counts for each view in an average exposure time of 100 seconds. If necessary, mild sedation udth diphenhydramine hydrochloride or hydroxyzine hydrochloride may be used. We ordinarily prefer the rectilinear scans in order that the life-sized liver image may be accurately superimposed on radiographs of the abdomen obtained in the scanning position. In addition, our own work suggests that the ability to detect filling deVol. 77, No. 2, pp. 211-215
2 12
O'Mara and McA[ee
fects in the liver is greater with a rectilinear scanner t h a n with a n Anger camera.
CASE REPORTS Case 1: Patient C. W. A 3-year-old girl entered the hospital with a 3 day history of fever, vomiting, and irritability. One day prior to admission she developed marked dyspnea. At the time of admission temperature was 104 ~ F. and respiratory rate was 42 per minute. Physical examination revealed a sick, irritable child. The lungs were clear to percussion and auscultation. The abdomen was tense with questionable tenderness in the right upper quadrant. The liver was barely palpable. Hemoglobin concentration was 7.1 Gin. per 100 ml., hematocrit was 27 per cent, and white blood cell count was 11,800 per cubic millimeter with a normal differential. A chest radiograph showed clear lung fields. However, when these radiographs were compared to one obtained 4 months previously, when the patient had a right upper lobe pneumonia, enlargement of the liver shadow was noted. An intravenous urogram was considered normal. A liver scan was performed with 1 millicurie of Tc-99m sulfur colloid. This demonstrated hepatomegaly with a large lateral filling defect (Fig. 1, A and B). Following the liver scan, it was thought that the patient's liver edge had become readily palpable and had certainly increased from 36 hours before.
The Journal o[ Pediatrics August 1970
At surgery 400 c.c. of purulent material was dranied from a large central abscess and several smaller satellite abscesses that closely surrounded it. Coagulase-positive Staphylococcus aureus was cultured. Postoperatively the patient had repeated bouts of pneumonia and right lower lobe atelectasis. These cleared with conventional therapy and the child completely recovered clinically. Case 2: Patient J. T. This 10-year-old Caucasian boy was admitted to an outlying community hospital with a spiking fever. Two days previously, he had fallen in a gym class and complained of pain in the right side. The provisional diagnosis was pneumonia. He was treated with antibiotics, but the fever persisted. On the twelfth day following the trauma, he was transferred to Memorial Hospital. Pulse was 120 per minute, respirations 40 per minute, temperature 102.4 ~ F. He was frightened and irritable. The liver was not palpable but there were guarding and mild tenderness in the right upper quadrant. No rebound tenderness could be elicited. The results of the remainder of the physical examination were within normal limits. The white blood cell count was 14,000 per cubic millimeter with a mild shift to the left. White blood cells were found in the urine. The patient was placed on antibiotic therapy. Chest radiographs and intravenous urograms were considered
Fig. 1. Case 1. A, An abdominal radiograph taken at time of scanning for localization p~rposes. B, Anterior projection of liver-lung scintillation scan demonstrating hepatomegaly and lateral filling defect in right lobe of liver. Operation revealed this to be an abscess. (The three black dots correspond to lead markers placed on abdomen and seen in Fig. 1, A. Diaphragms have been drawn in for reference.)
Volume 77 Number 2
to be normM. A liver scan, performed with 2.5 millicuries of Tc-99m sulfur colloid, demonstrated a large filling defect in the right lobe (Fig. 2, A, B, and C). A liver abscess was found at surgery which was incised and drained. The culture of the drainage revealed coagulase-posirive Staphylococcus aureus. The patient had an uneventful postoperative course and was discharged in good condition two weeks after surgery.
Scintillation scanning in hepatic abscess
2 13
DISCUSSION Pyogenic abscesses fortunately are relatively r a r e i n children. However, the diagnosis is difficult a n d frequently not m a d e until late in the course of the disease. Infectious agents m a y enter the liver via several routes: (1) b l o o d borne by w a y of the h e p a t i c artery, the p o r t a l vein, or, in infants, the umbilical vein; (2) inoculation t h r o u g h surgical incision o r open w o u n d ; or (3) direct invasion f r o m
Fig. 2. Case 2. A, Radiograph of abdomen demonstrating apparent hepatomegaly. B, Anterior projection of liver scan confirlning hepatosplenomegaly with large defect aIong lateral border of right lobe. C, Lateral projection of scan showinG absces.~ to be anterior to midplane of the lateral surface of the right lobe.
2 14
O ' M a r a and M c A [ e e
surrounding structures. I n some cases, the method of transmission is never found. D e h n e r and Kissane 2 state that systemic bacteremia is the most important mechanism in the development of hepatic abscess in children. I n adults, on the other hand, the most c o m m o n cause of pyogenic abscess is invasion from contiguous structures, especially by ascent of bacteria from an obstructed, infected biliary tract, s, 4 T h e most c o m m o n organisms in children are Staphylococcus aureus, Pseudomonas aeruginosa, and the Klebsiella group. At times, no organism m a y be identified. I n a review of cases over a 30 year interval, Sherm a n and Robbins ~ found that while the incidence of Escherichia coli and other gramnegative organisms in abscesses remained stable, the incidence of staphylococcus and streptococcus nearly doubled during the last 20 years of the study. As a rule, hepatomegaly is present. This may be due to an associated lesion such as biliary obstruction or leukemia. T h e abscesses may be solitary but are usually multiple. Abscesses m a y be found elsewhere in the body in over half the cases? Surgical drainage and antibiotics are the treatment of choice. T h e mortality rate tends to be high, possibly because of the delay in reaching a diagnosis. 5 T h e liver scan is a simple, safe procedure that is adaptable to the pediatric age group, s I t is valuable for both indicating the diagnosis and localizing the lesions prior to surgical drainage. T h e agents of choice, if avail-
The Journal o[ Pediatrics August 1970
able, are Tc-99m sulfur colloid or In-113m hydroxide colloid. ~ These short-lived radionuclides offer considerable advantage over the older agents, such as A u z98 colloid or I z~z microaggregated albumin, because of the reduction in radiation dose. Comparison of the total body and liver radiation dose estimates for 100 microcuries of A u 19s colloid and 1 millicurie of T c - 9 9 m sulfur colloid in the 1 year, 5 year, and adult age groups may be found in Table I, A and B. These calculations were obtained using the absorbed fraction method. 8 T h e values published by Seltzer and associates 9 were derived using the older classical formulas which usually give a somewhat lower radiation dose level than those obtained with the absorbed fraction method. No matter which method is used for calculations, the use of the shorter lived agent results in a marked reduction in radiation dose despite the administration of six times the amount of activity. These radioactive colloids are taken up in the reticuloendothelial cells of the liver, spleen, and bone marrow. O n e m a y observe increased activity in the spleen and bone m a r r o w accompanied by decreased concentration in the liver when there is gross impairment of hepatic blood flow. A liver scan gives information concerning size, shape, and position of the o r g a n ? ~ Accurate assessment of position is especially important in diagnosing subdiaphragmatic and subhepatic abscesses, particularly in relation to the right diaphragm, gas-filled loops of
TabIe I Colloidal Au t98 (rads/lO0 microcuries I.V.) References 1 yr. [ 5 yr. [ Adult A. Comparison of radiation dose estimates to the liver Present report 15,5 8.97 2.94 Seltzer et al. 9 20 12 4 Smith aa --2.6-4.3 B. Comparison of radiation dose estimates for total body Present report '0.817 0.462 Seltzer et al. 0 0.22 0.14 Smith 13 ---
0.132 0.054 0.234
Tc-99m sulfur colloid (fads~1 millicurie 1.V.) 1 yr. [ 5 yr. [ Adult
1.13
0.690
0.280
--
--
0.24-0.33
0.077
0.046
0.016
--
--
0.017
Volume 77 Number 2
adjacent bowel, and right kidney? 1 A radiograph of the abdomen is essential to properly assess displacement of the liver. Scanning m a y be used also to evaluate the liver following trauma. I n hepatic malignancies, it is a reliable guide to the efficacy of therapy and to the selection of sites for needle or open biopsy. Most important, as illustrated by the two cases presented, scanning demonstrates filling defects within the liver and m a y be used to direct the surgeon where to look for these. T h e r e are two basic limitations in the technique of hepatic scanning. First, the resolution limits the detection of lesions to those greater than 1.75 cm. in diameter at the periphery and 2 cm. in diameter in the central portion of the right lobe of a liver p h a n t o m filled with T c - 9 9 m sulfur colloid, using a 5 inch crystal scannerl~; lesions smaller than this are missed by scanning. A previous study indicates that spherical defects in a liver p h a n t o m are demonstrated better with T c - 9 9 m than with Au~gS.~2 Second, the presence of a zone of decreased or absent radioactivity on a liver scan is nonspecific in nature. T h e causes of such defects are many, including abscess, primary or secondary neoplasms, cysts, cavernous hemangiomas, trauma, amyloid deposits, dilated bile ducts, and postradiation or surgical defects. O n e must use the clinical history, physical examination, and other laboratory and radiographic findings in an attempt to deduce the cause of these defects on a scan. SUMMARY
Hepatic scintiscanning is a safe, rapid procedure which is capable of providing a great deal of information in the search for liver
Scintillation scanning in hepatic abscess
2 15
abscesses when considered in the proper clinical setting and with recognition of its limitations. REFERENCES
1. Harper, P. V., Lathrop, K., and Richards, P.: Technetium-99m as a radio colloid, J. Nuel. Med. 5: 382, 1964. 2. Dehner, L. P., and Kissane, J. M.: Pyogenic hepatic abscesses in infancy and childhood, J. PEDIAT. 74: 763, 1969. 3. Willard, J. H.: Pyogenic (non-amebic) abscess of the liver, in Bockus, H. L., editor: Gastroenterology, vol. 3, Philadelphia, 1965, W. B. Saunders Company, p. 487. 4. Sherman, J. D., and Robbins, S. L.: Changing trends in the causisitics of hepatic abscess, Amer. J. Med. 28: 9143, 1960. 5. Joseph, W. K., Kahn, A. M., and Longmire, W. P., Jr.: Pyogenic abscess--changing patterns of approach, Arner. J. Surg. 115: 63, 1968. 6. Tefft, M.: Radioisotopes in malignancies in children, J. A. M. A. 207: 1853, 1969. 7. Goodwin, D. A., Stern, H. D., Wagner, H. N., Jr., and Kramer, N. H.: New radiopharmaceutical for liver scanning, Nucleonics 24: 65, 1966. 8. Ellett, W. H., Callahan, A. B., and Brownell, G. L.: Gamma-ray dosimetry of internal emitters--Monte Carlo calculations of absorbed dose from point sources, Brit. J. Radiol. 37: 45, 1964. 9. Seltzer, R. A., Kerelakes, J. G., and Saenger, E. L.: Radiation exposure from radioisotopes in pediatrics, New Eng. J. Med. 271: 84, 1964. 10. McAfee, J. G., Ause, R. G., and Wagner, H. N., Jr.: Diagnostic value of scintillation scanning of the liver, Arch. Int. Med. 116: 95, 1965. 11. O'Mara, R. E.: Hepatic scintlscanning, New York J. Med. 68: 3021, 1968. 12. Loken, M. K., and Gerding, D.: Visualization of filling defects in a liver phantom containing Tc-99m, Hg-197, 1-131, or Au-198 using a rectilinear scanner or scintillation camera, Amer. J. Roentgen. 101: 551, 1967. 13. Smith, E. M.: Internal dose calculation for Tc-99m, J. Nucl. Med. 6: 231, 1965.
211
Scintillation scanning in the diagnosis of hepatic abscess in children Liver scintiscanning has been widely used in adults [or the diagnosis and localization of intrahepatic lesions. The use of this modality in children with liver abscess is discussed and illustrated.
Robert E. O'Mara, M.D., and John G. McAfee, M.D. SYRAGUStg~
N.
Y.
o f liver abscess is f r e difficult in children. The complaints are often nonspecific and the diagnosis usually reached by exclusion after considerable delay. There may be no history of a predisposing event such as trauma. Fever (often listed as of unknown origin), leukocytosis, abdominal discomfort or pain, sometimes localized to the right upper quadrant, and irritability comprise the most common presenting findings. Although hepatic radioisotopic imaging is widely used in adults for the diagnosis of focal hepatic lesions, it has seldom been mentioned in the pediatric literature. Two brief case histories are therefore presented as an illustration of how the hepatic scintiscan may pinpoint the diagnosis of hepatic abscess. In addition, a technique of hepatic imaging for children is described briefly. T g ~
DI A G N O S I S
quently
MATERIALS AND METHODS Technetium-99m sulfur colloid was selected as the agent of choice for hepatic imaging. From the Division o[ Nuclear Medicine, Department of Radiology, Upstate Medical Center, State University of New York.
This is easily prepared in the laboratory 1 and is also commercially available in kit form (Tesuloid Kit, Squibb Division of Nuclear Medicine, New Brunswick, N. J.). A dose of 1 to 3 millicuries, depending on the child's age and weight, was administered intravenously. The scans were obtained on a scanner with two opposing 5 inch crystal detectors, permitting two projections to be obtained simultaneously. Average scanning time is about 30 minutes for anterior, posterior, and both lateral projections. When a child is seriously ill, restless, or uncooperative, rectilinear scanning is not satisfactory because of motion artifacts. In this situation, scintiphotos may be obtained more quickly and easily with an Anger camera obtaining 300,000 counts for each view in an average exposure time of 100 seconds. If necessary, mild sedation udth diphenhydramine hydrochloride or hydroxyzine hydrochloride may be used. We ordinarily prefer the rectilinear scans in order that the life-sized liver image may be accurately superimposed on radiographs of the abdomen obtained in the scanning position. In addition, our own work suggests that the ability to detect filling deVol. 77, No. 2, pp. 211-215
2 12
O'Mara and McA[ee
fects in the liver is greater with a rectilinear scanner t h a n with a n Anger camera.
CASE REPORTS Case 1: Patient C. W. A 3-year-old girl entered the hospital with a 3 day history of fever, vomiting, and irritability. One day prior to admission she developed marked dyspnea. At the time of admission temperature was 104 ~ F. and respiratory rate was 42 per minute. Physical examination revealed a sick, irritable child. The lungs were clear to percussion and auscultation. The abdomen was tense with questionable tenderness in the right upper quadrant. The liver was barely palpable. Hemoglobin concentration was 7.1 Gin. per 100 ml., hematocrit was 27 per cent, and white blood cell count was 11,800 per cubic millimeter with a normal differential. A chest radiograph showed clear lung fields. However, when these radiographs were compared to one obtained 4 months previously, when the patient had a right upper lobe pneumonia, enlargement of the liver shadow was noted. An intravenous urogram was considered normal. A liver scan was performed with 1 millicurie of Tc-99m sulfur colloid. This demonstrated hepatomegaly with a large lateral filling defect (Fig. 1, A and B). Following the liver scan, it was thought that the patient's liver edge had become readily palpable and had certainly increased from 36 hours before.
The Journal o[ Pediatrics August 1970
At surgery 400 c.c. of purulent material was dranied from a large central abscess and several smaller satellite abscesses that closely surrounded it. Coagulase-positive Staphylococcus aureus was cultured. Postoperatively the patient had repeated bouts of pneumonia and right lower lobe atelectasis. These cleared with conventional therapy and the child completely recovered clinically. Case 2: Patient J. T. This 10-year-old Caucasian boy was admitted to an outlying community hospital with a spiking fever. Two days previously, he had fallen in a gym class and complained of pain in the right side. The provisional diagnosis was pneumonia. He was treated with antibiotics, but the fever persisted. On the twelfth day following the trauma, he was transferred to Memorial Hospital. Pulse was 120 per minute, respirations 40 per minute, temperature 102.4 ~ F. He was frightened and irritable. The liver was not palpable but there were guarding and mild tenderness in the right upper quadrant. No rebound tenderness could be elicited. The results of the remainder of the physical examination were within normal limits. The white blood cell count was 14,000 per cubic millimeter with a mild shift to the left. White blood cells were found in the urine. The patient was placed on antibiotic therapy. Chest radiographs and intravenous urograms were considered
Fig. 1. Case 1. A, An abdominal radiograph taken at time of scanning for localization p~rposes. B, Anterior projection of liver-lung scintillation scan demonstrating hepatomegaly and lateral filling defect in right lobe of liver. Operation revealed this to be an abscess. (The three black dots correspond to lead markers placed on abdomen and seen in Fig. 1, A. Diaphragms have been drawn in for reference.)
Volume 77 Number 2
to be normM. A liver scan, performed with 2.5 millicuries of Tc-99m sulfur colloid, demonstrated a large filling defect in the right lobe (Fig. 2, A, B, and C). A liver abscess was found at surgery which was incised and drained. The culture of the drainage revealed coagulase-posirive Staphylococcus aureus. The patient had an uneventful postoperative course and was discharged in good condition two weeks after surgery.
Scintillation scanning in hepatic abscess
2 13
DISCUSSION Pyogenic abscesses fortunately are relatively r a r e i n children. However, the diagnosis is difficult a n d frequently not m a d e until late in the course of the disease. Infectious agents m a y enter the liver via several routes: (1) b l o o d borne by w a y of the h e p a t i c artery, the p o r t a l vein, or, in infants, the umbilical vein; (2) inoculation t h r o u g h surgical incision o r open w o u n d ; or (3) direct invasion f r o m
Fig. 2. Case 2. A, Radiograph of abdomen demonstrating apparent hepatomegaly. B, Anterior projection of liver scan confirlning hepatosplenomegaly with large defect aIong lateral border of right lobe. C, Lateral projection of scan showinG absces.~ to be anterior to midplane of the lateral surface of the right lobe.
2 14
O ' M a r a and M c A [ e e
surrounding structures. I n some cases, the method of transmission is never found. D e h n e r and Kissane 2 state that systemic bacteremia is the most important mechanism in the development of hepatic abscess in children. I n adults, on the other hand, the most c o m m o n cause of pyogenic abscess is invasion from contiguous structures, especially by ascent of bacteria from an obstructed, infected biliary tract, s, 4 T h e most c o m m o n organisms in children are Staphylococcus aureus, Pseudomonas aeruginosa, and the Klebsiella group. At times, no organism m a y be identified. I n a review of cases over a 30 year interval, Sherm a n and Robbins ~ found that while the incidence of Escherichia coli and other gramnegative organisms in abscesses remained stable, the incidence of staphylococcus and streptococcus nearly doubled during the last 20 years of the study. As a rule, hepatomegaly is present. This may be due to an associated lesion such as biliary obstruction or leukemia. T h e abscesses may be solitary but are usually multiple. Abscesses m a y be found elsewhere in the body in over half the cases? Surgical drainage and antibiotics are the treatment of choice. T h e mortality rate tends to be high, possibly because of the delay in reaching a diagnosis. 5 T h e liver scan is a simple, safe procedure that is adaptable to the pediatric age group, s I t is valuable for both indicating the diagnosis and localizing the lesions prior to surgical drainage. T h e agents of choice, if avail-
The Journal o[ Pediatrics August 1970
able, are Tc-99m sulfur colloid or In-113m hydroxide colloid. ~ These short-lived radionuclides offer considerable advantage over the older agents, such as A u z98 colloid or I z~z microaggregated albumin, because of the reduction in radiation dose. Comparison of the total body and liver radiation dose estimates for 100 microcuries of A u 19s colloid and 1 millicurie of T c - 9 9 m sulfur colloid in the 1 year, 5 year, and adult age groups may be found in Table I, A and B. These calculations were obtained using the absorbed fraction method. 8 T h e values published by Seltzer and associates 9 were derived using the older classical formulas which usually give a somewhat lower radiation dose level than those obtained with the absorbed fraction method. No matter which method is used for calculations, the use of the shorter lived agent results in a marked reduction in radiation dose despite the administration of six times the amount of activity. These radioactive colloids are taken up in the reticuloendothelial cells of the liver, spleen, and bone marrow. O n e m a y observe increased activity in the spleen and bone m a r r o w accompanied by decreased concentration in the liver when there is gross impairment of hepatic blood flow. A liver scan gives information concerning size, shape, and position of the o r g a n ? ~ Accurate assessment of position is especially important in diagnosing subdiaphragmatic and subhepatic abscesses, particularly in relation to the right diaphragm, gas-filled loops of
TabIe I Colloidal Au t98 (rads/lO0 microcuries I.V.) References 1 yr. [ 5 yr. [ Adult A. Comparison of radiation dose estimates to the liver Present report 15,5 8.97 2.94 Seltzer et al. 9 20 12 4 Smith aa --2.6-4.3 B. Comparison of radiation dose estimates for total body Present report '0.817 0.462 Seltzer et al. 0 0.22 0.14 Smith 13 ---
0.132 0.054 0.234
Tc-99m sulfur colloid (fads~1 millicurie 1.V.) 1 yr. [ 5 yr. [ Adult
1.13
0.690
0.280
--
--
0.24-0.33
0.077
0.046
0.016
--
--
0.017
Volume 77 Number 2
adjacent bowel, and right kidney? 1 A radiograph of the abdomen is essential to properly assess displacement of the liver. Scanning m a y be used also to evaluate the liver following trauma. I n hepatic malignancies, it is a reliable guide to the efficacy of therapy and to the selection of sites for needle or open biopsy. Most important, as illustrated by the two cases presented, scanning demonstrates filling defects within the liver and m a y be used to direct the surgeon where to look for these. T h e r e are two basic limitations in the technique of hepatic scanning. First, the resolution limits the detection of lesions to those greater than 1.75 cm. in diameter at the periphery and 2 cm. in diameter in the central portion of the right lobe of a liver p h a n t o m filled with T c - 9 9 m sulfur colloid, using a 5 inch crystal scannerl~; lesions smaller than this are missed by scanning. A previous study indicates that spherical defects in a liver p h a n t o m are demonstrated better with T c - 9 9 m than with Au~gS.~2 Second, the presence of a zone of decreased or absent radioactivity on a liver scan is nonspecific in nature. T h e causes of such defects are many, including abscess, primary or secondary neoplasms, cysts, cavernous hemangiomas, trauma, amyloid deposits, dilated bile ducts, and postradiation or surgical defects. O n e must use the clinical history, physical examination, and other laboratory and radiographic findings in an attempt to deduce the cause of these defects on a scan. SUMMARY
Hepatic scintiscanning is a safe, rapid procedure which is capable of providing a great deal of information in the search for liver
Scintillation scanning in hepatic abscess
2 15
abscesses when considered in the proper clinical setting and with recognition of its limitations. REFERENCES
1. Harper, P. V., Lathrop, K., and Richards, P.: Technetium-99m as a radio colloid, J. Nuel. Med. 5: 382, 1964. 2. Dehner, L. P., and Kissane, J. M.: Pyogenic hepatic abscesses in infancy and childhood, J. PEDIAT. 74: 763, 1969. 3. Willard, J. H.: Pyogenic (non-amebic) abscess of the liver, in Bockus, H. L., editor: Gastroenterology, vol. 3, Philadelphia, 1965, W. B. Saunders Company, p. 487. 4. Sherman, J. D., and Robbins, S. L.: Changing trends in the causisitics of hepatic abscess, Amer. J. Med. 28: 9143, 1960. 5. Joseph, W. K., Kahn, A. M., and Longmire, W. P., Jr.: Pyogenic abscess--changing patterns of approach, Arner. J. Surg. 115: 63, 1968. 6. Tefft, M.: Radioisotopes in malignancies in children, J. A. M. A. 207: 1853, 1969. 7. Goodwin, D. A., Stern, H. D., Wagner, H. N., Jr., and Kramer, N. H.: New radiopharmaceutical for liver scanning, Nucleonics 24: 65, 1966. 8. Ellett, W. H., Callahan, A. B., and Brownell, G. L.: Gamma-ray dosimetry of internal emitters--Monte Carlo calculations of absorbed dose from point sources, Brit. J. Radiol. 37: 45, 1964. 9. Seltzer, R. A., Kerelakes, J. G., and Saenger, E. L.: Radiation exposure from radioisotopes in pediatrics, New Eng. J. Med. 271: 84, 1964. 10. McAfee, J. G., Ause, R. G., and Wagner, H. N., Jr.: Diagnostic value of scintillation scanning of the liver, Arch. Int. Med. 116: 95, 1965. 11. O'Mara, R. E.: Hepatic scintlscanning, New York J. Med. 68: 3021, 1968. 12. Loken, M. K., and Gerding, D.: Visualization of filling defects in a liver phantom containing Tc-99m, Hg-197, 1-131, or Au-198 using a rectilinear scanner or scintillation camera, Amer. J. Roentgen. 101: 551, 1967. 13. Smith, E. M.: Internal dose calculation for Tc-99m, J. Nucl. Med. 6: 231, 1965.