Step 1: Understanding the Question.
A toddler fed mostly on dilute cow's milk, which is watered down and low in protein, develops long standing diarrhea and then swelling of the feet. We need the most likely diagnosis.
Step 2: Key Concept.
Kwashiorkor is a form of severe protein energy malnutrition where the diet is poor in protein even though total calories may be near adequate. Low protein intake leads to low blood albumin, and low albumin drops the pressure that normally holds fluid inside blood vessels, so fluid leaks into the tissues and causes swelling, most often seen first in the feet. Diarrhea is both common in these children and worsens the protein loss further.
Step 3: Detailed Explanation.
Option (A), Kwashiorkor, fits perfectly. A diet of dilute cow's milk supplies little protein, and the resulting low albumin explains the feet swelling on top of the long diarrhea.
Option (B), acute renal failure, would usually show reduced urine output and abnormal kidney tests, not just a dietary history and edema of the feet.
Option (C), congestive cardiac failure, would come with breathing difficulty, a fast heart rate, and an enlarged liver, none of which are described here.
Option (D), Indian childhood cirrhosis, is a liver disease usually linked to excess copper exposure, often from copper or brass vessels, and it presents with an enlarged liver and jaundice rather than this feeding history.
Step 4: Final Answer.
The dietary history of protein poor dilute milk plus feet swelling points clearly to Kwashiorkor.
\[ \boxed{\text{Kwashiorkor}} \]