Bacterial infections causing spontaneous bacterial peritonitis, sepsis, and cellulitis may complicate nephrotic syndrome from FSGS. Episodes of peritonitis typically manifest with abdominal pain, rebound tenderness, guarding, and anorexia with or without fever. The diagnosis can be confirmed by performing a paracentesis, which demonstrates leukocytosis of the peritoneal fluid with a predominance of neutrophils and a positive peritoneal fluid culture. The most common causes of peritonitis in patients with nephrotic syndrome are Streptococcus pneumoniae, Escherichia coli, and a variety of Gram-negative rods. The exclusion of alternate abdominal pathology is critical as a ruptured appendix, for example, may also present with abdominal pain, rebound tenderness, and guarding.