A healthy 6-year-old girl was referred for a single day of diarrhoea (2 episodes) along with 3 episodes of involuntary anal orangey discharge that stained her trousers. Her stool was also remarked to be watery, orange-brown and oily. She complained of having some abdominal cramps, but was otherwise well, with no nausea, fever or dehydration. Appetite remained good. Her parents (and the girl) could not remember when she had last passed stools but it appeared to be at least 3 days ago. Clinical examination was unremarkable.

There was no recent history of travel. Her parents had eaten the same food for the past three days but had no related symptoms. Although they had eaten out a few times during the course of the week, these were at restaurants and did not involve raw food. No one else in the family has been unwell (including the pet dog). 

Questions

1. What is the pertinent exposure history to elicit and what is the diagnosis?

[Updated 25th June 2017]

This is a condition known as keriorrhea. There are no diagnostic tests – the symptoms and history are characteristic (although taking the anti-obesity drug orlistat comes close). It is caused by consumption of fish such as oilfish and escolar.

The fish’s diet comprises esters that they cannot digest, and which are distributed throughout the flesh of the fish. This makes for a pleasant “buttery” taste, but the waxy esters (gempylotoxin) also cannot be digested by humans, and will emerge unchanged as an orangey, oily anal discharge anytime between half an hour to 1.5 days after the meal. Other symptoms have also been reported, including abdominal cramps and actual diarrhoea. Keriorrhea is socially discomforting, but there is no real physical risk – there is no dehydration as with other causes of diarrhoea. The only known ways of minimising the risk are to consume less than 170 grams of fish and grill the fish thoroughly, draining off all the oil before serving.

The fish is banned from consumption in Japan, South Korea and Italy. Our Agri-food and Veterinary Authority (AVA) assessed the issue in 2004 and 2007, but rightly did not issue any ban, only recommending public education and correct labelling. This last part is very important as escolar – being a cheap fish – is often mislabeled and sold as more expensive fish in restaurants around the world, including Singapore. It has been mislabeled (deliberately) as white tuna, cod, seabass, and butterfish (although in Singapore, AVA seems to permit this designation). The microbiologist at 10minus6cosm will provide a more thorough update on fish (mis)labelling at a later date.