**Question:** Most common cause of nosocomial urinary tract infection -

A. Urethritis
B. Prostatitis
C. Cystitis
D. Pyelonephritis

**Core Concept:** Nosocomial infections are those that occur in hospitalized patients after admission and are not present or incubating at the time of admission. Urinary tract infections (UTIs) are a common complication in hospitalized patients due to prolonged catheterization, lack of hygiene, and immunosuppression.

**Why the Correct Answer is Right:** Nosocomial UTIs are typically caused by bacteria that have gained entry into the urinary tract system through the urethra during catheterization or due to contamination. Among the given options, **D. Pyelonephritis** is the correct answer because it is a severe form of UTI that involves the kidneys and can lead to serious complications if left untreated.

**Why Each Wrong Option is Incorrect:**

A. **Urethritis (Urethritis)** is an inflammation of the urethra, not a UTI. Although it can lead to ascending infection, it is not the most common cause of nosocomial UTIs.

B. **Prostatitis** is an inflammation of the prostate gland, not a UTI. While it can lead to UTIs, it is not the most common cause in nosocomial settings.

C. **Cystitis** is an inflammation of the bladder, not a UTI. Although it can lead to UTIs, it is not the most common cause of nosocomial UTIs.

**Clinical Pearl:** Proper catheterization technique, hygiene, and timely removal of catheters can prevent many nosocomial UTIs. Monitoring patients for symptoms and signs of UTIs is essential in early detection and treatment.