## **Core Concept**
Tubercular pyelonephritis is a form of renal tuberculosis that primarily affects the kidneys. The infection usually results from the hematogenous spread of Mycobacterium tuberculosis from a primary focus, commonly in the lungs. This condition predominantly affects the renal cortex and medulla.

## **Why the Correct Answer is Right**
The correct answer, **Hemogenous**, is right because tubercular pyelonephritis typically occurs through the hematogenous route. After a primary infection, usually in the lungs, Mycobacterium tuberculosis enters the bloodstream and is carried to the kidneys, where it establishes a focus of infection. This hematogenous spread allows the bacteria to seed in the renal cortex, leading to the development of tubercular pyelonephritis.

## **Why Each Wrong Option is Incorrect**
- **Option A: Direct spread** - This option is incorrect because, although direct spread from adjacent organs can occur in some cases of abdominal tuberculosis, it is not the typical route for tubercular pyelonephritis.
- **Option B: Lymphatic** - This option is incorrect because lymphatic spread is not the primary route for the dissemination of tuberculosis to the kidneys.
- **Option C: Ascending** - This option is incorrect because ascending infection is more commonly associated with bacterial urinary tract infections rather than tubercular pyelonephritis.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that renal tuberculosis often presents with sterile pyuria (presence of white blood cells in the urine without bacterial growth on routine culture) and may have systemic symptoms like fever and weight loss. A high index of suspicion is necessary for diagnosis, especially in endemic areas.

## **Correct Answer: D. Hemogenous**