What is the most likely cause of an abdominal mass in a 5-month-old with other notable symptoms?

In a 5-month-old infant presenting with an abdominal mass, Wilms' tumor is considered a likely cause due to its prevalence and the typical age of onset. Wilms' tumor, a type of kidney cancer, often presents as a palpable abdominal mass in children, particularly within the age range of 2 to 5 years, making this age group a critical period for diagnosing such tumors.

The presence of additional notable symptoms, such as hypertension, hematuria, or abdominal swelling, can further support the suspicion of Wilms' tumor. Its common clinical presentation and the age of the patient align well with the characteristics of this tumor, thus making it a primary consideration in differential diagnoses when an abdominal mass is encountered.

Other options, while they may also present with abdominal masses or other symptoms, are less common in a 5-month-old. For example, a hernia, while possible, typically presents differently and may not manifest as a significant abdominal mass. Appendicitis is quite rare in infants this young and more commonly occurs in older children. A mesenteric cyst, although it can occur in young children, is also considered uncommon compared to the well-established risk of Wilms' tumor in infants. Therefore, the characteristics of Wilms'