While stomach pain and diarrhea are not the typical presentation for most common sexually transmitted infections (STIs), specific pathogens transmitted through sexual contact can directly target the digestive system. Infections like chlamydia and gonorrhea primarily affect the urogenital tract, but other STIs may cause gastrointestinal (GI) distress as a secondary result of a systemic illness or widespread immune response. Understanding this distinction is important for seeking appropriate diagnosis and treatment from a medical professional.
Direct Pathogens Affecting the Digestive Tract
Infections causing gastroenteritis, typically associated with contaminated food or water, can also be transmitted sexually, particularly through oral-anal contact. These sexually transmitted enteric pathogens primarily act on the gut lining, leading to acute abdominal symptoms.
Parasitic Infections
The parasitic infection Giardiasis, caused by Giardia duodenalis, targets the small intestine. Symptoms often include severe stomach cramps, bloating, nausea, and watery, foul-smelling diarrhea that may last for several weeks. Amoebiasis, caused by Entamoeba histolytica, directly invades the intestinal wall. Individuals with amoebiasis may experience severe, crampy abdominal pain, weight loss, and diarrhea that can sometimes be bloody.
Bacterial and Viral Infections
Bacterial infections like Shigellosis are highly contagious and transmitted through sexual activity involving fecal-oral contamination. Shigellosis causes acute symptoms such as fever, abdominal pain, and profuse diarrhea. Viral infections that target the liver, such as Hepatitis A, are also transmitted via the fecal-oral route and can be sexually acquired. Hepatitis A causes inflammation of the liver, leading to GI symptoms in the pre-jaundice phase of the illness. These symptoms include nausea, loss of appetite, and abdominal discomfort, often felt in the upper right quadrant where the liver is located.
Systemic STIs Causing Secondary Gastrointestinal Distress
Some STIs cause stomach pain and diarrhea as a secondary effect of the body’s response to a systemic infection, rather than by infecting the gut directly.
HIV
Acute HIV infection, the initial stage of the virus, often presents with flu-like symptoms that include gastrointestinal upset. Diarrhea is a frequent complaint during this seroconversion period, typically starting one to two weeks after exposure. This GI distress results from the body mounting an intense immune response and the initial infiltration of the virus into the lymphoid tissue of the bowel wall. For individuals with untreated HIV that progresses to an advanced stage, the weakened immune system allows for opportunistic infections to take hold. Pathogens such as Cytomegalovirus (CMV) or Mycobacterium avium complex (MAC) can severely colonize the GI tract, causing severe, chronic diarrhea, abdominal pain, and profound weight loss.
Syphilis
Syphilis, caused by Treponema pallidum, is a systemic infection that can affect organs outside of the genital tract, particularly during its secondary stage. The systemic inflammation caused by syphilis can involve the liver, leading to syphilitic hepatitis. This liver involvement can manifest as generalized abdominal discomfort. Syphilis can also cause inflammation in the stomach (gastritis) or rectum (proctitis), resulting in upper abdominal pain or painful bowel movements.
Testing and Consulting a Healthcare Provider
Because stomach pain and diarrhea are common symptoms of many non-sexually transmitted illnesses, connecting them to a sexual exposure requires a specific diagnostic approach. The first and most important step is providing a thorough and honest sexual history to a healthcare provider. This discussion should include details about the types of sexual activity, particularly any oral-anal contact, and the timing of recent exposures relative to the onset of symptoms.
Diagnosis often involves a combination of testing methods based on the suspected pathogen. For the direct enteric infections like Giardiasis or Amoebiasis, a healthcare provider will typically request a stool sample. This sample is analyzed under a microscope or with specific molecular tests to identify the presence of the parasites or bacteria. Systemic STIs require blood testing to confirm the diagnosis, detecting antibodies for HIV, Syphilis, and Hepatitis A. Timely diagnosis is necessary because early treatment can significantly reduce the risk of long-term complications and prevent further transmission. Anyone experiencing persistent GI symptoms after a potential exposure should seek medical consultation immediately.

