**Question:** True about nephrogenic rest -

a) Associated with Wilm's tumor
b) Increased risk of Wilm's tumor in contralateral kidney
c) No association with Wilm's tumor
d) Abnormal embryonal renal tissue

**Correct Answer:**

**Core Concept:** Nephrogenic rest is a developmental anomaly characterized by the presence of abnormal embryonic renal tissue in an adult kidney. This tissue is derived from the metanephric mesenchyme and can coexist with normal renal parenchyma. Nephrogenic rest is a precursor to Wilm's tumor, a rare kidney malignancy in children.

**Why the Correct Answer is Right:**

Nephrogenic rest is indeed associated with Wilm's tumor. It is a precursor lesion for Wilm's tumor, which is a childhood kidney cancer. The abnormal embryonic renal tissue found in nephrogenic rest can undergo malignant change over time, leading to the development of Wilm's tumor.

**Why Each Wrong Option is Incorrect:**

a) Associated with Wilm's tumor: Correct
b) Increased risk of Wilm's tumor in contralateral kidney: Incorrect - Nephrogenic rest itself is not associated with an increased risk of Wilm's tumor in the contralateral kidney. It is a localized lesion.
c) No association with Wilm's tumor: Incorrect - As mentioned above, nephrogenic rest is associated with Wilm's tumor.
d) Abnormal embryonal renal tissue: Correct - Nephrogenic rest is characterized by the presence of abnormal embryonic renal tissue in the adult kidney.

**Why the Correct Answer is Right:**

Nephrogenic rest is an embryonic renal remnant that can progress to Wilm's tumor in some cases. Wilm's tumor is a childhood kidney cancer that arises from the abnormal embryonic renal tissue in nephrogenic rest.

**Why Each Wrong Option is Incorrect:**

a) Increased risk of Wilm's tumor: Incorrect - As mentioned, nephrogenic rest is associated with Wilm's tumor but does not directly cause an increased risk in the contralateral kidney.
b) No association with Wilm's tumor: Incorrect - Nephrogenic rest is associated with Wilm's tumor.
c) Abnormal embryonal renal tissue: Correct - Nephrogenic rest is characterized by the presence of abnormal embryonic renal tissue.
d) No abnormal embryonal renal tissue: Incorrect - Nephrogenic rest is characterized by the presence of abnormal embryonic renal tissue.