Abdominal distension is common in kwashiorkor, and many reasons have been proposed for it [1,2]:
Dilated bowel loops (because of gas produced by bacterial overgrowth),
An enlarged liver (because of steatosis, i.e. fat accumulation),
Ascites, i.e. excess fluid in the peritoneal cavity (as part of the
generalised oedema of kwashiorkor), and
Weakness of the ...
The Gastroenterology paper you cite doesn't mention distended bellies at all. There is no dispute that fatty liver is a symptom of kwashiorkor. But the Wikipedia article makes it quite clear that the cause of the distended belly is edema.
The extreme lack of protein causes an osmotic imbalance in the gastro-intestinal system causing swelling of the gut ...