Primary Peritonitis without Abdominal Signs Causing a Diagnostic Dilemma: A Case Report

Introduction

Primary peritonitis is a spontaneous, diffuse, suppurative infection of the peritoneum with no identifiable intra-abdominal source. Historically, the incidence of primary peritonitis has significantly decreased-from approximately 10% of pediatric abdominal emergencies in the pre-antibiotic era to less than 1% today. Over time, shifts have been observed not only in its incidence but also in the mean age of onset, predominant causative organisms, and associated mortality rates. Typically, primary peritonitis presents with abdominal pain, fever, and vomiting.^1,2 Here, however, we report an unusual presentation of a common condition where a child presented with fever, loose stools, and non-bilious vomiting without abdominal pain or other classical abdominal signs, exemplifying an atypical presentation that can complicate diagnosis and management.

Case Report

A six-year-old female presented to the emergency department with three days of fever, loose stools, and non-bilious vomiting but no abdominal pain, distension, or urinary symptoms. Upon examination, she appeared ill with a heart rate of 100/min, blood pressure of 86/50 mmHg, and signs of dehydration (dry mucous membranes). Cardiovascular and respiratory system examinations were normal. Her abdomen was flat, with mild tenderness in the hypogastric region, normal bowel sounds, and no organomegaly.

Initial lab work showed a normal leukocyte count (10.8 x 10⁹/L) and a positive C-reactive protein (CRP). Urine analysis revealed pyuria, leading to a provisional diagnosis of urinary tract infection (UTI). She received intravenous fluids and antibiotics, and her urine culture grew Escherichia coli, sensitive to the prescribed antibiotics. Follow-up evaluations as per the Indian Academy of Pediatrics UTI protocol revealed moderate ascites on abdominal ultrasound, with no abnormalities in the kidneys, ureters, or bladder.³

Despite initial treatment, the child remained febrile, though her loose stools and vomiting subsided. A follow-up blood count indicated leukocytosis (23.1 x 10⁹/L) with neutrophilic predominance, elevated CRP, and toxic granules on the peripheral smear. Repeated abdominal ultrasound showed increased ascites, prompting a diagnostic tap, which revealed purulent fluid. Chest X-ray showed no pneumoperitoneum, while an erect abdominal X-ray displayed multiple air-fluid levels (Figure 1). The diagnosis of pyoperitoneum was made, necessitating emergency laparoscopy.

Due to diffuse adhesions, laparoscopy was converted to laparotomy, revealing an abdomen filled with pus and flakes (Figure 2). After adhesiolysis and pus evacuation, no hollow viscus perforation was found. Examination of the uterus, fallopian tubes, and ovaries showed normal findings, confirming primary peritonitis. Peritoneal lavage was performed, and a pelvic drain was placed. Postoperatively, oral feeds resumed after 72 hours, with a gradual return to a regular diet. Both Gram stain and peritoneal fluid culture were sterile. The postoperative recovery was smooth, and the drain was removed on the sixth day before discharge. The child continues to thrive on follow-up.

Discussion

Primary peritonitis is a spontaneous, and diffuse infection of the peritoneum with no identifiable intra-abdominal source.¹ Incidence, mortality, age demographics, and bacterial profiles of primary peritonitis have shifted over recent decades due to advances in antibiotics.⁴ Generally, children with specific risk factors, such as nephrotic syndrome, liver cirrhosis, or immunodeficiencies, are more susceptible, but in this case, our patient presented with no known risk factors.

Studies report primary peritonitis to be most common in children aged 6-10 years, with a higher incidence in girls (4:1 ratio).^5,6 The peritoneum can be invaded through several routes: (1) ascending infection from the genital tract, (2) transdiaphragmatic lymphatics, (3) the gastrointestinal tract, and (4) the bloodstream.⁷ Typical symptoms include abdominal pain, fever, and vomiting. Sen et al., observed that abdominal pain was present in 93.5% of cases and distension in 85% cases of primary peritonitis.⁸ In our case, the absence of abdominal pain or classic signs like guarding delayed diagnosis, as initial workup pointed toward a urinary tract infection.

Physical examination often reveals tenderness in 25%- 72% of cases,with common signs like rebound tenderness and guarding; white blood cell counts can exceed 20 x 10⁹/L, less common signs include acute scrotal swelling and periumbilical erythema.^1,9 In this case, however, the patient exhibited none of these signs, and her leukocyte count was normal on admission. Only after observing persistent symptoms and ascites did we pursue an ascitic tap, which indicated pyoperitoneum and guided further intervention.

Primary peritonitis diagnosis requires exclusion of other causes, using imaging or surgical exploration if needed. Culturing peritoneal fluid typically identifies a single organism in 90% of cases studies, highlighted Streptococcus pneumoniae and Streptococcus spp. as prevalent pathogens, though gram-negative bacteria and even viruses are increasingly implicated.2,10 Treatment usually involves broad-spectrum antibiotics and peritoneal drainage, with surgical exploration to verify the infection source if necessary. The introduction of antibacterial agents and timely surgical intervention has resulted in a dramatic decrease in the morbidity and mortality of primary peritonitis.

Primary peritonitis often presents atypically, which can complicate timely diagnosis and management, resulting in significant morbidity. Surgeons and primary care physicians should consider primary peritonitis as a potential diagnosis even in otherwise healthy children, especially when symptoms are nonspecific. Early diagnosis and timely intervention are essential to mitigate morbidity and mortality in these cases, ensuring effective management and improved outcomes.

Conflict of Interest

The authors have no conflicts of interest relevant to this article to disclose.

Written Consent

Obtained from the parents for the publication.