**Core Concept:** Urinary tract infections (UTIs) are a group of infections that affect any part of the urinary system, including the kidneys, ureters, bladder, and urethra. Gross hematuria, or visible blood in the urine, can be a symptom of a UTI.

**Why the Correct Answer is Right:** The correct answer is option D, Urinary Tract Infection (UTI). In this scenario, the patient develops gross hematuria 3 days after an attack of UTI. Gross hematuria is a symptom of a UTI because the infection causes inflammation and damage to the urinary tract tissues, leading to bleeding.

**Why Each Wrong Option is Incorrect:**

A. Kidney stones (renal calculi): Although kidney stones can cause hematuria, they typically present with flank pain, chills, and fever, which are not mentioned in the question.

B. Prostatic enlargement (benign prostatic hyperplasia): Gross hematuria in a male patient due to prostatic enlargement usually presents with obstructive symptoms like frequency, urgency, and nocturia rather than hematuria presenting 3 days post-infection.

C. Chronic kidney disease: Hematuria in chronic kidney disease is usually due to glomerular filtration failure rather than an acute infection-induced inflammation.

D. Urinary Tract Infection (UTI): As explained earlier, UTIs can cause hematuria due to the inflammation and tissue damage in the urinary tract. In this case, hematuria presents 3 days post-infection.

**Clinical Pearl:** A timely diagnosis and treatment of UTI can prevent complications and reduce morbidity. Prompt utilization of appropriate antibiotics can lead to successful management and recovery of the patient.