Gastrointest Radiol 17:271-273 (1992)

Gastrointestinal-

Radiology 9 Springer-VerlagNew York Inc. 1992

Silent Rectal Perforation After Endoscopic Polypectomy: CT Features Ba D. Nguyen and Irwin Beckman Department of Diagnostic Radiology, Allegheny General Hospital and The Medical College of Pennsylvania, Pittsburgh, Pennsylvania, USA

Abstract. A case of silent extraperitoneal rectal perforation secondary to coionoscopic polypectomy is presented. Computed tomography (CT) demonstrated pathways of gas diffusion from the perirectal site to different compartments of the retroperitoneum, to the mediastinum and peritoneum. Key words: Colonoscopy, complications--Rectum, perforation--Retroperitone gas, CT diagnosis.

Perforation resulting from colonoscopy-polypectomy ranges from 0.5-3% [1-4]. Multiple reports on this complication described the isolated or combined presence of gas in the retroperitoneum, mediastinum, and peritoneum. Most complications were supported by conventional radiography [5-8]. We describe a patient with silent rectal perforation following polypectomy, presenting with gas in different spaces of the abdomen on computed tomography

Physical examination showed a chronically ill patient with orthostatic hypotension and sinus tachycardia. The lungs were clear with questionable decreased breath sounds at both bases. The abdomen was soft, protuberant, and diffusely tender with no evidence of peritonitis. The routine chest film revealed significant pneumoperitoneum with pneumomediastinum and subcutaneous emphysema. The supine abdominal film revealed the presence of gas in the retroperitoneum outlining the right kidney and the lateral border of the psoas muscle. Further assessment with CT demonstrated the presence of gas in the perirectal and presacral spaces dissecting upward along the lilac vessels (Fig. IA and B). Gas in the retroperitoneum dissected the pararenal space outlining the right kidney, adrenal, and ureter (Fig, IC). There was extension to the posterior pararenal space with propagation to the lateral properitoneal fat. More cephalad images showed gas over the bare area of the liver, right anterolateral aspect of the inferior vena cava (IVC), and peritoneum outlining the falciform ligament and superior coronary ligament (Fig. 1D). CT confirmed a pneumomediastinum with gas coming from the retroperitoneum via the diaphragmatic hiatus. Extensive subcutaneous emphysema was also noted. The patient, with essentially no abdominal symptoms, was treated conservatively and her pneumoperitoneum resolved after several days of observation.

(CT). Case Report A 67-year-old woman was admitted with a history of increasing dyspnea and generalized weakness due to chronic obstructive pulmonary disease. Three days prior to the admission, she had a sigmoidoscopy for rectal bleeding. The study found a 1.5-cm semisessile polyp at 10 cm in the rectum, which was removed by snare cautery and recovery for pathology. The base of the polyp was cauterized with good hemostasis. The histologic examination revealed an adenomatous polyp with focal adenocarcinoma in situ.

Address offprint requests to: Irwin Beckman, D.O., Department of Diagnostic Radiology, Allegheny General Hospital, 320 East North Avenue, Pittsburgh, PA 15212, USA

Discussion A potential complication of colonoscopy and polypectomy is bowel perforation which occurs in 0.53% of cases [1-4]. Perforation may result from electrocautery of large sessile polyps, transmural burns secondary to unintentional extension of heat beyond the base of the polyps, and snare wire entrapment in either polyp or colonic wall leading to coagulation necrosis [6]. The predominant site of perforation is at the rectum and sigmoid colon [2, 4, 6]. Due to the subperitoneal location of the rectum, the extravasation of gas or fluid mainly involves the extraperitoneal tissue. The gas diffusion conforms to the anat-

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B. Nguyen and 1. Beckman: Silent Extraperitoneal Rectal Perforation

Fig, 1. A C T scan shows gas in the perirectal and presacral space following rectal perforation (arrow). R, rectum. B Extraperitoheal gas is noted in the retrocecal space (arrow) and around the right lilac vessels (arrowheads). P, pneumoperitoneum. C CT scan shows gas in the perirenal and posterior pararenal space. There is dissection of the properitoneal fat with subcutaneous emphysema (arrowhead). Gas outlines the right kidney IRK) and right ureter tarrow). P, pneumoperitoneum. D CT scan through the liver shows extraperitoneal gas outlining the superior coronary ligament (arrow), bare area of the liver (arrowheads), and right anterolateral aspect of the IVC. Retrocrural gas spreads to the mediastinum.

omy and characteristics of the extraperitoneal spaces which consist of three compartments [9, 10]: 1. The anterior pararenal space, between the posterior parietal peritoneum and anterior renal fascia, contains the pancreas, duodenal loop, and ascending and descending colon.

2. The perirenal space, between the anterior and posterior renal fasciae or Gerota's fascia, contains the kidney, adrenal gland, proximal collecting system, and renal vessels. 3. The posterior pararenal space, between the posterior renal fascia and transversalis fascia, contains no organ and continues laterally with the properitoneal fat. Caudally, these three spaces are in continuity with each other and with the pelvic extraperitoneal tissue in the region of the iliac fossa. The posterior pararenal space continues cephalad as subdiaphragmatic fat. The right perirenal or anterior pararenal compartment communicates with the bare area of the liver and intrahepatic portion of the IVC [9-12]. The extraperitoneal space, composed of loose areolar and connective tissue, is characterized by low distensibility [5]. Excess gas in this space sec-

B. Nguyen and I. Beckman: Silent Extraperitoneal Rectal Perforation

ondary to rectal perforation is forced out in two directions following the previously described anatomy. Horizontally, the expansion dissects the posterior pararenal compartments toward the properitoneal fat stripe causing subcutaneous emphysema. Vertically, gas diffusion involves preferentially the posterior pararenal space [9], sometimes both retroperitoneal compartments with extension upward to the mediastinum via the diaphragmatic hiatus, and downward to the scrotum, groin, or lower extremities through the inguinal area [5, 7, 11]. Extraperitoneal gas spread also depends upon the site of the rectal perforation. Midline extravasation will enter the retroperitoneum bilaterally. Lateral leak, similar to our case, will selectively involve one side [9]. Our case had a concomittent pneumoperitoneum most likely secondary to perforation of the posterior parietal peritoneum [5]. It has been stressed that the retroperitoneum is less sensitive to sepsis than the peritoneum and that the extraperitoneal gas spread is remarkable for the benign clinical course [6, 8]. As seen in our case, nonsurgical treatment is best when the patient remains clinically stable [3].

References 1. Reiertsen O, Skjoto J, Jacobsen CD, Rosseland AR. Complications of fiberoptic gastrointestinal endoscopy. Five years' experience in a central hospital. Endoscopy 1987:19:1-6

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2. Nivatvongs S. Complications in colonoscopic polypectomy: lessons to learn from an experience with 1576 polyps. Am Surg 1988;54:61-63 3. Carpio G, Albu E, Gumbs MA, Gerst PH. Management of colonic perforation after colonoscopy. Report of three cases. Dis Colon Rectum 1989;32:624-626 4. Soon JCC, Shang NS, Goh PMY, Rauff A. Perforation of large bowel during colonoscopy in Singapore. Am Surg 1990;56:285-288 5. Calenoff L, Poticha SM. Combined occurrence of retropneumoperitoneum and pneumoperitoneum. A JR 1973; 117:366-372 ' 6. Ostyn B, Bercoff E, Manchon ND, Louvel JP, Janvresse A, Michot F, Bourreille J. Retroperitoneal abscess complicating colonoscopy polypectomy. Dis Colon Rectum 1987;30:201203 7. Lezak MB, Goldhamer M. Retroperitoneal emphysema after colonoscopy. Gastroenterology 1974;66:118-120 8. Schmidt G, Borsch G, Wegener M. Subcutaneous emphysema and pneumothorax complicating diagnostic colonoscopy. Dis Colon Rectum 1986;29:136-138 9. Meyers MA. Radiological features of the spread and localization of extraperitoneal gas and their relationship to its source. Radiology 1974:117:17-26 10. Love L, Meyers MA, Churchill RJ, Reynes CJ, Moncada R, Gibson D. Computed tomography of extraperitoneal spaces. A JR 1988;136:781-789 11. Kneeland JB, Auh YH, Rubenstein WA, Zirinsky K, Morrison H, Whalen JP, Kazam E. Perirenal spaces: CT evidence for communication across the midline. Radiology 1987; 164:657-664 12. Lira JH, Auh YH, Suh S J, Kim KW. Right perirenal space: computed tomography evidence of communication between the bare area of the liver. Clin Imag 1990;14:239-244

Received: September 10, 1991; accepted: October 28, 1991