In a febrile child fulfilling the diagnostic criteria for Kawasaki disease who now has jaundice and diarrhea, what is the underlying cause of these findings?

Jaundice and Diarrhea in Kawasaki Disease

Jaundice and diarrhea in this febrile child with Kawasaki disease are direct manifestations of the systemic vasculitis affecting the gastrointestinal system and liver, representing recognized non-cardiac complications of the acute inflammatory process.

Underlying Pathophysiology

The gastrointestinal and hepatic findings in Kawasaki disease result from the widespread systemic vasculitis that characterizes this condition. While coronary arteries are the most clinically significant target, the inflammatory process affects multiple organ systems simultaneously during the acute phase 1.

Gastrointestinal Manifestations

Diarrhea is a common gastrointestinal manifestation occurring in approximately one-third of patients with Kawasaki disease 1. The American Heart Association guidelines explicitly list diarrhea among the recognized gastrointestinal findings, along with vomiting and abdominal pain 1. These symptoms result from:

• Intestinal inflammation and edema secondary to vasculitis affecting the mesenteric vessels 2
• Bowel wall involvement that can progress to more severe complications like intestinal pseudo-obstruction, though this is less common 1, 3
• The systemic inflammatory state causing altered intestinal motility and function 2

Hepatobiliary Manifestations

Jaundice in Kawasaki disease reflects hepatic involvement with hepatitis and cholestasis 1. The American Heart Association guidelines specifically recognize both "mild jaundice" and "mild increase of serum transaminase levels" as documented gastrointestinal findings 1. The mechanisms include:

• Hepatitis from direct vasculitic inflammation of hepatic vessels, causing hepatocellular injury and elevated transaminases 1
• Cholestatic jaundice that can present as acute febrile cholestatic jaundice in some cases 4
• Gallbladder hydrops (acute acalculous distention), which occurs in approximately 15% of patients during the first 2 weeks and can contribute to biliary obstruction 1

Clinical Context and Recognition

These findings are part of the broader spectrum of "other significant clinical and laboratory findings" that support the diagnosis but are not part of the principal diagnostic criteria 1. The presence of gastrointestinal symptoms can actually complicate diagnosis:

• Prominent gastrointestinal symptoms may lead to surgical admission with other Kawasaki features being overlooked, representing a common diagnostic pitfall 5
• Some children may even present as an acute surgical abdomen, though this is rare 1
• Hepatic enlargement frequently accompanies the jaundice 1

Important Clinical Caveats

The gastrointestinal and hepatic manifestations typically resolve with appropriate treatment of the underlying Kawasaki disease 2. Key points include:

• These findings reflect the acute inflammatory phase and should improve with IVIG and aspirin therapy 2
• The presence of jaundice and diarrhea does not change the fundamental treatment approach, which remains high-dose IVIG and aspirin 1
• Persistent or worsening gastrointestinal symptoms after IVIG may indicate treatment resistance and warrant consideration of second-line therapies 6
• Hypoalbuminemia commonly accompanies the gastrointestinal involvement and contributes to the clinical picture 2

Do not mistake these gastrointestinal symptoms for a separate infectious or surgical condition—they are integral manifestations of the systemic vasculitis in Kawasaki disease 1, 5.