Fig. 1. Mechanisms of PTB development.

There are three main pathways through which TB infects the peritoneum. In most cases, the bacterial spread is achieved by reactivation of TB in the lungs (or other solid organs) and subsequent hematogenous or lymphatic spread to the peritoneum (depicted in 1). Though rare, peritoneal infection by the intestinal tract is possible due to the ingestion of infected milk or sputum. In this pathway, the TB infects the mucosal layer of the gastrointestinal tract, with subsequent formation of epithelioid tubercles in the lymphoid tissue of the submucosa. Caseous necrosis of the tubercles in roughly 2–4 weeks leads to mucosal ulceration and can lead to infection of deeper layers of the intestines and eventually into adjacent lymph nodes and peritoneum (depicted in 2). The third pathway of peritoneal infection involves the direct spread to the peritoneum from an infected adjacent focus, such as the fallopian tubes (pictured) or a psoas abscess74 (depicted in 3). The icons were adapted from flaticon.com. Abbreviations: PTB, peritoneal tuberculosis; TB, tuberculosis.