Which is the most likely diagnosis for a patient presenting with severe rectal bleeding and a low hemoglobin level?

In the case of a patient presenting with severe rectal bleeding and low hemoglobin levels, the most likely diagnosis is a bleeding diverticulum. This condition often leads to significant blood loss, especially if the diverticulum is inflamed or has eroded into a blood vessel. The association of severe rectal bleeding with a low hemoglobin level indicates a substantial volume of blood loss, which is characteristic of diverticular bleeding, particularly in individuals with diverticular disease.

Diverticula are pouches that can form in the colon wall, and when they bleed, it can result in acute and often profuse hematochezia (bright red blood in the stool). The low hemoglobin level further supports the idea of acute blood loss. While other conditions could also cause rectal bleeding, the severity of the bleeding and the resulting anemia align closely with what is typically seen in a bleeding diverticulum.

Other options, while also possible causes of rectal bleeding, tend to present differently or with less acute blood loss. Carcinoma of the colon may cause rectal bleeding, but it generally presents with other symptoms over time and does not always lead to such immediate and drastic drops in hemoglobin. Meckel's diverticulum typically causes bleeding in younger patients and presents