A 69-year-old female with known metastatic malignant melanoma presented with a three-week history of vomiting, altered bowel habit, abdominal distension and passing altered blood per rectum. An eighteen-month history of generalized abdominal pain, weight loss and anorexia were also noted. Prior to these three months, she had a similar obstructive episode. Computed tomography (CT) scan demonstrated metastatic deposits within the liver and on the serosa of the small bowel. This was managed conservatively with resolution of symptoms.

Clinical findings on the second presentation were: a distended, tympanic abdomen with no signs of peritonism. Initial bloods tests revealed a microcytic anemia and an elevated inflammatory response, but no signs of renal impairment or electrolyte imbalance.

Repeat CT scan revealed disease progression and a 'target shaped lesion' consistent with an intussuscepting small bowel loop within the right iliac fossa. (Figure 1A-B) Laparotomy revealed four metastatic deposits within the small bowel. One lesion had caused obstruction due to complete intussusception, one had caused a partial intussusception and the remaining two were non-obstructing serosal lesions. (Figure 2) The segment of small bowel containing all four lesions was excised by a wedge resection and continuity was restored with an end-to-end anastomoses.

In pediatric patients intussusception is the second most common cause of abdominal emergencies and is idiopathic in 95% of cases. [1] In contrast, it is rare in the adult population, accounting for only 1% of bowel obstruction and is frequently attributed to neoplasia. [2] Malignant melanoma is a locally invasive disease with a high capacity for metastasis. Metastatic spread is initially through the lymphatic system with distant metastases as a late feature .[3] The gastrointestinal tract represents one of the most common sites for metastatic spread of melanoma. The jejunum and ileum are particularly vulnerable to deposition. [4] Metastatic deposits are either submucosal, causing small bowel obstruction and potential ulceration; or polypoid, which can become a lead point for intussusception. [3] [5]

In any patient with a history of malignant melanoma and non-specific gastrointestinal symptoms, including small bowel obstruction, the possibility of a small bowel metastases should be considered. This case illustrates the varying progression of metastatic lesions within the small bowel from serosal deposition, through to partial and complete intussusception.

Katrina Butcher – Registrar performing the operation

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