Surgical Site Infection (SSI): This is the most likely diagnosis given the symptoms of leakage from the surgical site and abdominal pain. SSIs are a common complication of abdominal surgery and can lead to leakage of pus or other fluids from the wound.

Dehiscence: This refers to the partial or complete separation of previously closed surgical incisions, which can lead to leakage of intestinal contents or other fluids. It is a plausible diagnosis given the symptoms.
Intra-abdominal Abscess: An abscess is a collection of pus that can form in the abdomen after surgery, leading to pain and potentially leakage if it ruptures or drains through the surgical site.
Adhesions or Bowel Obstruction: Although these conditions might not directly cause leakage, they can lead to abdominal pain and potentially complicate the healing process of the surgical site, indirectly contributing to leakage.

Necrotizing Fasciitis: A severe infection that affects the tissue beneath the skin and the fascia, a layer of tissue covering muscles, nerves, fat, and blood vessels in the affected area. It is rare but deadly if not promptly treated.
Perforated Viscus: A hole in one of the organs in the abdomen (like the stomach or intestine) can lead to leakage of contents into the abdominal cavity, causing severe pain and potentially life-threatening peritonitis.
Hemorrhage: Internal bleeding in the abdominal cavity can cause pain and, if severe, lead to shock and death. While it might not directly cause leakage from the surgical site, it's a critical condition that requires immediate attention.

Fistula Formation: An abnormal connection between two body parts, such as between the intestine and the skin, which can cause leakage of intestinal contents. This is a less common complication but can occur after abdominal surgery.
Evisceration: A rare but serious condition where the intestines or other organs protrude through the surgical wound, requiring immediate medical attention.