Urinary Tract Infection (UTI): The combination of abdominal pain, which could be related to the lower abdomen, and alkaline urine, which can occur due to the infection altering the urine's pH, makes UTI a plausible diagnosis. The bacteria in a UTI can split urea into ammonia, increasing the urine's pH.

Kidney Stones: While kidney stones can cause severe abdominal pain and potentially alter urine pH, the direct link to alkaline urine is less common. However, the pain associated with stones can radiate to the abdomen.
Pyelonephritis: An infection of the kidney, which can cause abdominal pain and potentially alter urine characteristics, including pH, due to the infection's impact on renal function.

Appendicitis: Although appendicitis primarily causes abdominal pain and does not directly cause alkaline urine, it's a critical diagnosis not to miss due to the potential for severe complications if untreated. The pain can sometimes be confused with urinary tract issues.
Sepsis: In cases where an infection leads to sepsis, abdominal pain can be a symptom, and urinary output and characteristics can be altered. Sepsis is life-threatening and requires immediate attention.

Milk-Alkali Syndrome: A condition caused by excessive ingestion of calcium and alkali, leading to hypercalcemia, metabolic alkalosis, and renal impairment. It could potentially cause abdominal pain and alter urine pH.
Medullary Sponge Kidney: A rare congenital disorder that affects the kidneys and can lead to the formation of small cysts in the inner part of the kidneys, potentially causing urinary abnormalities, including changes in urine pH, and abdominal pain due to kidney stones or infection.