Diagnosis

Richters' hernia at the trocar site causing small bowel obstruction. An enhanced CT scan of the patient's abdomen showed dilated loops of small bowel with no passage of contrast to the colon. The subcutaneous lucency at the trocar site was felt to represent unresorbed post-operative air (figure 1). A barium enema was performed to evaluate the anastomosis. A spot-film tangential to the abdominal wall (figure 2) showed a collapsed loop of small bowel (black arrow) incorporated into the trocar site. The lucency leading from the contrast-filled bowel to the staples represents the hernia tract (arrowheads). At surgery, a length of small bowel (approximately 2 cm) was found incarcerated between the peritoneum and the external oblique muscle. The hernia was reduced without injury and the defect was repaired.

Discussion

Complications of laparoscopic surgery are uncommon,^1,2 and may be directly related to the type of surgery performed (e.g., bile duct injury during laparoscopic cholecystectomy) or to the laparoscopic entry itself. Complicatons to the latter include abdominal wall bleeding, omental bleeding, abdominal vessel injury, bladder and bowel perforation, solid visceral injury, and infection.^3,4 Trocar site hernias occur infrequently, with a reported incidence of 1 to 3.6%.^5,6 However, some authors claim that trocar site hernias are under-reported and that the incidence is probably somewhat higher.^5,6 Even when trocar site hernias are asymptomatic they can result in small bowel obstruction.⁶ Occasionally the hernia responsible for the obstruction is the Richters' type.⁵ Richters' hernias result when a knuckle of bowel becomes lodged in a small opening, classically the femoral canal.² Richters' hernias also can occur at trocar sites because of a small (10 to 15 mm) defect left after trocar sheath removal.^2,5 Generally, the bowel lumen remains patent, resulting in partial obstruction. Consequently, surgical repair may be delayed, increasing the possibility of partial thickness bowel infarction, perforation, and resulting peritonitis.² Richters' hernias are difficult to diagnose preoperatively because they generally have no palpable mass and there is no obvious herniation of a bowel loop on CT. As with our case, the clinical picture is often confusing in that a post-laparoscopic patient presents with bowel obstruction of unclear etiology. Patient presentation of small bowel obstruction due to trocar site hernia from one day to one year after surgery has been reported.^5,6 Others may remain occult for longer periods of time.⁷ It seems reasonable that the radiologist should consider a trocar site hernia in any post-laparoscopic patient presenting with small bowel obstruction regardless of the time since surgery. A knowledge of the technical aspects of laparoscopic surgery and standard locations of trocar sites will allow careful inspection of both plain films and CT scans. This may lead to early diagnosis, which can help guide operative repair alternatives, such as utilizing a local approach instead of exploratory laparotomy. In addition, the possibility of bowel ischemia may be reduced with early intervention. Lastly, with the rise in the number and complexity of laparoscopic procedures performed, an increased awareness of this entity is important, as these characteristic hernias will be encountered in greater numbers.

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2. Hass B, Schrager R: Small bowel obstruction due to Richters' hernia after laparoscopic procedures. J Laparoendosc Surg 3:421- 423, 1993.
3. Ray C, Hibbein J, Wilbur A: Complications after laparoscopic cholecystectomy: Imaging findings. AJR 160:1029-1032, 1993.
4. Wright T, Bertino R, Bishop A, et al: Complications of laparoscopic cholecystectomy and their interventional radiologic management. Radiographics 13:119-128, 1993.
5. Plaus W: Laparoscopic trocar site hernias. J Laparoendosc Surg 3:567-570, 1993.
6. Boike G, Miller C, Spirtos N, et al: Incision bowel herniations after operative laparoscopy: A series of nineteen cases and review of the literature. Am J Obstet Gynecol 172:1726-1733, 1995.
7. Miller P, Mezwa D, Feczko P, et al: Imaging of abdominal hernias. Radiographics 15:333-347, 1995.