Complicated colonic intussusception.

The manuscript deals with the case of a 53-year-old woman who developed large bowel obstruction. Per-rectal examination revealed a pedunculated lesion in the rectum; rigid sigmoidoscopy revealed a prolapsing pedunculated mass with a necrotic surface. The patient recovered well following anterior resection. Histology confirmed a pedunculated sub mucosal lipoma as the lead point for intussusception. Colonic intussusception is a rare cause of adult large bowel obstruction, and the preoperative clinical diagnosis of this condition can be difficult. Resection of the involved segment of the colon is the most appropriate choice of treatment in most such cases.

INTRODUCTION

Intussusception is a common cause of bowel obstruction in pediatric population. Intussusception in adult is a rare condition, which is often difficult to diagnose.

CASE REPORT

A 53-year-old woman developed large bowel obstruction with symptoms that arose 48 hours before presentation. She had visited the emergency department once 2 years before the current episode because of mass prolapsing through the rectum. However, the condition resolved before she was even examined in the emergency department. Per-rectal examination upon the current presentation revealed a pedunculated lesion in the rectum whose upper extent was beyond the reach of the finger. Rigid sigmoidoscopy revealed a prolapsing pedunculated mass with a necrotic surface. Computed tomography (CT) scan confirmed the diagnosis of intussusception [Figure 1]. During the operation, chronic intussusception was identified, with an irreducible intussusceptum starting at the level of the proximal sigmoid colon and reaching to the level of the mid-rectum [Figure 2]. Anterior resection was performed with primary stapled anastomosis. The patient recovered well following surgery, and was discharged on the fifth day. Histology confirmed a pedunculated sub-mucosal lipoma as the lead point for intussusception.

Figure 1

CT scan image showing target lesion of colonic intussusception

Figure 2

Operative specimen of colon showing lipoma as lead point of intussusception

DISCUSSION

Intussusception is an unusual cause of bowel obstruction in adults, accounting for just 1% of all cases. Unlike in the pediatric population, intussusception in adults has an initiating pathological cause in up to 90% of cases. Begos et al. analyzed 1048 cases of adult intussusception and reported that only 29% of adult colonic intussusceptions were caused by benign lesions.[1] Lipoma is the second most common benign colonic lesion. Weinberg et al. reported an incidence of gastrointestinal lipomas of 5.8%, based on their autopsy series.[2] They also found that the colon is the most common part of the gastrointestinal tract to develop a lipoma. Colonic lipomas are usually small and asymptomatic. Lipoma as a cause of colonic intussusception is a rare but known entity.

Clinical diagnosis of intussusception is difficult. Unlike in children, adults present with a variety of symptoms, which can be chronic or acute. CT scan is considered the most useful imaging modality to confirm the diagnosis of intussusception. The target lesion observed on CT or ultrasound scan is indicative of the intussusceptum surrounded by the edematous intussuscipiens. This early lesion may progress to an amorphous mass as bowel necrosis sets in. CT scan can also help to identify the causative lesion producing the intussusception. A lesion with a radio-density similar to that of fat just distal to the target lesion is suggestive of a lipoma as the lead point for intussusception. However, this finding may change depending on the degree of infarction and fat necrosis present. In fact, Buetow et al. reported that only 1 in 10 colonic intussusceptions caused by lipoma showed fat-attenuation, whereas the remaining cases had densities varying from half-fat to pure soft-tissue densities.[3]

Lipomas less than 20 mm in diameter are usually asymptomatic and are often discovered inadvertently during colonoscopy. Observation of the tent sign (mucosa can be elevated with biopsy forceps over lipoma), pillow sign (lesion can be indented with the biopsy forceps), or naked fat sign (fat can be extruded from the lesion after serial biopsy) help to confirm the diagnosis of lipoma during endoscopy. Such small lesions can be safely removed endoscopically. However, symptomatic lipomas of the colon require a more extensive intervention. The safety of endoscopic removal of larger lipomas is controversial, because of the possibility of invagination of the serosa in the stalk leading to free perforation. Geraci et al. reviewed reported cases in the literature and suggested that endoscopic resection of larger lipomas can be safely performed, though they reported 6 perforations following 46 resections.[4] In cases unsuitable for endoscopic resection, surgical resection of the involved segment is recommended for symptom relief and prevention of intussusception.

For established colonic intussusception, laparotomy is generally recommended. Colotomy and excision of the lesion is not generally recommended, unless the benign nature of the lead point is preoperatively confirmed. In addition, colotomy would have to be performed through a previously ischemic oedematous bowel. In irreducible intussusception, as observed in our case, such a procedure is not possible, even if the benign nature of the lesion has been confirmed. In adult colonic intussusception, because of the high proportion of malignant initiating lesions, resection of the involved segment of the bowel is generally recommended. For this reason, Azar et al.,[5] who examined 58 cases of adult intussusception, recommend a formal resection along the route of lymphatic drainage in all cases of adult intussusception. Operative reduction of colonic intussusception is also not recommended, because of the fear of possible transperitoneal seeding of the tumor.

CONCLUSION

Colonic lipoma, though is a benign condition in itself, can lead to intussusception. The preoperative clinical diagnosis of this condition can be difficult. Resection of the involved segment of the colon is the most appropriate choice of treatment in most such cases.