Persistent diarrhoea and occult vipomas in children

British Medical Journal, June 3, 2000 by M S Murphy, A Sibal, J R Mann

Lesson of the Week

Failure to recognise secretory diarrhoea leads to inappropriate gastrointestinal investigations, delayed diagnosis of a vipoma, and avoidable morbidity

A wide range of gastrointestinal disorders may cause chronic diarrhoea in childhood. In a small proportion of cases the diarrhoea is due to active intestinal fluid secretion--secretory diarrhoea. It is essential to identify such cases because of important diagnostic implications. Patients with unexplained persistent watery diarrhoea should undergo a period of fasting; continuing diarrhoea indicates a secretory process. Secretory diarrhoea is confirmed by a raised stool sodium concentration. In the developed world the most likely explanation for persistent secretory diarrhoea may be an occult vipoma--a tumour that secretes vasoactive intestinal polypeptide.[1, 2] This is an uncommon tumour. The first two cases described here presented 25 and 15 years ago respectively, and the remaining four presented in the past 10 years. As these reports illustrate, however, vipomas are amenable to curative surgery. If the diagnosis is not considered, extensive gastrointestinal investigations may be undertaken, the diagnosis will be delayed, and avoidable morbidity will occur.

Case reports

Case 1

An 18 month old boy presented with an eight month history of diarrhoea, malnutrition, and abdominal distension. During eight weeks of inpatient investigation only a xylose absorption test proved abnormal. Coeliac disease was suspected, and he received a gluten free diet without intestinal biopsy. He was lost to follow up until 28 months of age, when he presented with a respiratory infection. A chest radiograph showed a tumour in the pulmonary right upper zone. The diarrhoea had persisted and he was severely malnourished.

Case 2

A 1 year old boy was referred with a two month history of watery diarrhoea, malnutrition, and abdominal distension. Investigations were normal, but a gluten free diet was started without intestinal biopsy. There was no improvement. Treatment with metronidazole for unproved giardiasis was ineffective. A "hypoallergenic" diet was prescribed, but the symptoms continued. After four months in hospital a barium contrast study with small bowel follow through unexpectedly showed the tumour as a space occupying lesion in the rectum. This was palpable on digital rectal examination. He was referred to the department of paediatric surgery, and by then he was severely malnourished and hypokalaemic (potassium concentration 2.8 mmol/l).

Case 3

A 2 year old boy was referred with a four month history of watery diarrhoea and weight loss. He had already been on a diet free of cows' milk for six weeks. A mass was palpable in the left lower abdomen. Serum electrolytes were normal. He was referred to the department of oncology, and ultrasonography showed a calcified left paravertebral tumour.

Case 4

An 8 month old boy was referred with a six week history of watery diarrhoea and weight loss. He had been starved and given oral rehydration solution repeatedly. During four weeks of inpatient investigations a xylose absorption test was abnormal and jejunal biopsy showed mild villous atrophy. He began a gluten free diet, but the diarrhoea continued. He was referred to the department of gastroenterology, and by then was severely malnourished, and hypokalaemic (potassium 1.9 mmol/l). Parenteral nutrition was begun and enteral feeds were stopped, but the diarrhoea persisted. Abdominal ultrasonography showed a calcified tumour in the right suprarenal area.

Case 5

A 16 month old boy was referred with a six month history of diarrhoea and poor weight gain. Trials of cows' milk exclusion and loperamide had been unsuccessful. During exacerbations he had been starved and given oral rehydration solution repeatedly. Toddler diarrhoea was suspected. At review three months later, his parents reported persistent watery diarrhoea, and he was admitted for investigation. He was hypernatraemic (sodium 151 mmol/l) and hypokalaemic (potassium 2.6 mmol/l), with a metabolic acidosis (bicarbonate 14 mmol/l). A further trial of cows' milk exclusion was started, but the diarrhoea persisted. At age 26 months he was referred to the department of gastroenterology, and by then was severely malnourished, hypokalaemic, and acidotic. The stool sodium concentration was markedly raised (81 mmol/l). Abdominal ultrasonography showed a calcified left suprarenal tumour.

Case 6

A 1 year old girl was referred with a three week history of watery diarrhoea. Before referral kaolin suspension had been prescribed, and she was starved and given oral rehydration solution repeatedly. She was hypokalaemic (potassium 2.9 mmol/l). The diarrhoea persisted during a 48 hour fast, and the stool sodium concentration was grossly raised (120 mmol/l). Nevertheless, the post-gastroenteritis syndrome was suspected, and she was started on a lactose free, protein hydrolysate formula. The diarrhoea continued, and after three weeks she was transferred to the department of gastroenterology, by which time she was seriously malnourished. Insertion of a urinary catheter allowed confirmation of severe diarrhoea during a 48 hour period of fasting (80 g/kg/day). She was hypokalaemic (potassium 2.3 mmol/l) with a metabolic acidosis (bicarbonate 16 mmol/l). Abdominal ultrasonography showed a left suprarenal tumour (fig 1).