A woman with chronic constipation and diabetes presents with acute anal pain. What is the most likely diagnosis?

In the context of a woman with chronic constipation and diabetes experiencing acute anal pain, the most likely diagnosis is a perirectal abscess. This condition is characterized by the accumulation of pus in the perirectal area, typically resulting from infection, and can often occur in individuals with risk factors such as a history of anal fissures or other rectal pathology.

Patients with chronic constipation may suffer from straining, leading to trauma or micro-tears in the anal mucosa, increasing the risk of infection and subsequent formation of an abscess. Diabetes can further compromise immune function, making infections more likely to occur and complicating their resolution. The acute onset of pain is a hallmark of perirectal abscesses, as they can cause significant inflammation and tenderness in the affected area.

Understanding the symptomatology and risk factors associated with perirectal abscesses helps clarify why this diagnosis is appropriate in such a clinical scenario. In contrast, other conditions like anal fistulas, perianal hematomas, and thrombosed external hemorrhoids can also result in anal pain but often have distinct clinical presentations or are less commonly linked to chronic constipation and diabetes. Thus, perirectal abscess stands out as the most consistent diagnosis in this case.