Pathophysiology of Abdominal Pain in Henoch-Schönlein Purpura
Abdominal pain in children with HSP results from IgA-mediated leukocytoclastic vasculitis affecting the small vessels of the gastrointestinal tract, leading to bowel wall edema, submucosal hemorrhage, and ischemia. 1
Mechanism of Gastrointestinal Involvement
The underlying pathophysiology involves immune complex deposition that causes necrosis of small- and medium-sized arterial walls with neutrophil infiltration and nuclear fragmentation—a process called leukocytoclastic vasculitis. 1 This vasculitic process specifically targets the submucosal vessels of the GI tract, with IgA deposition demonstrable on intestinal biopsies. 1
The vasculitis-induced mucosal ischemia produces several pathological changes:
- Bowel wall edema and hemorrhage from vascular congestion and inflammation in the submucosal vessels 1
- Mucosal ulceration secondary to ischemic injury 1
- Vascular congestion causing increased intraluminal pressure and pain 1
Clinical Manifestations of the Vasculitic Process
The small bowel is the most frequently involved GI site, particularly the jejunum and ileum. 2, 1 This anatomic predilection explains the characteristic presentation:
- Periumbilical and epigastric pain that worsens with meals due to bowel angina (ischemia during increased metabolic demand) 1
- Diffuse colicky abdominal pain as the most common GI symptom, occurring in 50-75% of patients 2
- Occult or overt bleeding (melena) from mucosal hemorrhage and ulceration 1, 3
Severe Complications from Vasculitic Injury
The vasculitic process can lead to serious structural complications in 4.6% of cases:
- Intussusception (most common surgical complication), typically ileo-ileal or ileo-colic, caused by edematous bowel wall serving as a lead point 1, 4
- Bowel perforation (usually ileal), occurring spontaneously or associated with intussusception from transmural ischemia 1, 4
- Bowel wall thickening visible on imaging, particularly affecting the jejunum and ileum 1, 3
Important Clinical Pearls
Abdominal symptoms precede the characteristic purpuric rash in 14-36% of cases, which can lead to diagnostic confusion and unnecessary laparotomy when HSP mimics an acute surgical abdomen. 4 The pain results from active inflammation and ischemia, not from mechanical obstruction in most cases.
Ultrasonography is the investigation of choice because it can demonstrate bowel wall thickening, ascites, and intussusception (particularly small bowel intussusception that is inaccessible to contrast enema). 3, 4 When stool occult blood is 3+ or 4+, the incidence of positive imaging findings is high, indicating more severe vasculitic involvement. 3
The majority of patients improve spontaneously as the vasculitic process resolves, though the efficacy of corticosteroids in preventing severe complications remains controversial. 1