Dengue is one of the most common tropical diseases in Sri Lanka, presenting with abdominal pain and fever. Further, during dengue shock, hypovolemia also presents as severe abdominal pain [14]. Therefore, accurate and well-timed diagnosis of coexisting medical and surgical conditions such as acute appendicitis, acute pancreatitis, and cholecystitis is often difficult in dengue infection [11,12,13]. Children with predominant abdominal pain may be referred to surgeons initially, and dengue fever might be the underlying diagnosis subsequently, although it could potentially be detected with delay due to initial focus on the surgical abdomen [15]. Sometimes, an initial referral to the surgeon can lead to an unnecessary appendectomy [10]. Some authors suggest that acute abdomen may be a co-occurrence with dengue infection rather than a direct effect, although pathophysiological changes occurring in dengue may predispose to acute abdomen [15].
Lymphoid hyperplasia and mesenteric adenitis may also mimic acute appendicitis in dengue [16]. One of these reported children had enlarged multiple mesenteric lymph nodes in the first abdomen ultrasound, and subsequent ultrasound only showed ruptured acute appendicitis with abscess formation. The initial ultrasound findings misguided the clinical presentation as mesenteric adenitis and poorly visualized appendix instead of ruptured appendix. The pathophysiology of appendicitis in the context of dengue fever and its recovery is not clearly understood [17]. One potential etiology is lymphoid hyperplasia and mesenteric adenitis present in the febrile phase of dengue fever. The pathophysiological changes that occur during the onset of dengue hemorrhagic fever including systemic inflammatory response syndrome and plasma leakage are also likely to contribute to the development of acute abdomen including appendicitis [16]. Plasma leakage can result in an edematous appendix with luminal obstruction, promoting secondary bacterial infection and appendicitis [18]. Direct viral invasion can also lead to acute appendicitis. Other proposed mechanisms include endotoxemia and ischemic reperfusion injury [19].
A study in Pakistan showed that the incidence of acute abdomen in dengue fever had been 12% during the period of the dengue epidemic. Moreover, five of seven patients diagnosed with acute appendicitis underwent appendectomies, although histology did not favor their diagnosis. Therefore, accurate diagnosis is important to avoid unnecessary surgical procedures to reduce mortality [18]. A previously reported child in Sri Lanka revealed an appendicular mass occurring simultaneously with dengue infection [16]. Both of these children were diagnosed to have acute appendicitis during the recovery phase of DHF. The clinical presentation of case 1 was initially misinterpreted as acute bacillary dysentery due to high white blood cell count, high C-reactive protein, and normal abdomen ultrasound. However, careful consideration of alternative diagnoses and intense abdominal pain directed authors to repeat the ultrasound, which detected acute appendicitis. In the second case, although the first ultrasound was commented as acute mesenteric adenitis, increased abdominal pain and increased septic markers made the authors repeat the ultrasound by consultant radiologist.
Analyzing the clinical presentations of the two reported children in retrospect, it could be argued that the abdominal pain beyond the critical or viremia phase in dengue infection might be acute abdomen until proven otherwise. Therefore, an active survey of differential diagnoses is crucial to prevent morbidity and mortality of similar unexpected complications.