**Question:** Structures removed in RND dissection are all except:

A. Spleen
B. Pancreas
C. Kidney
D. Omentum

**Correct Answer:** D. Omentum

**Core Concept:** RND dissection involves removing the retroperitoneal structures, which include the retroperitoneal lymph nodes, blood vessels, nerves, and other tissues surrounding the retroperitoneal organs.

**Why the Correct Answer is Right:**

Retroperitoneal space is a potential space situated posterior to the abdominal organs and anterior to the spine. The structures removed during RND dissection primarily include the lymph nodes, blood vessels, and nerves surrounding the retroperitoneal organs. However, the omentum is an essential structure that is a part of the mesentery and connects the gastrointestinal tract to the abdominal wall. It plays a crucial role in protecting, nourishing, and stabilizing the gut, making it an essential structure that should not be removed during RND dissection.

**Why Each Wrong Option is Incorrect:**

1. **A. Spleen:** Although the spleen is a retroperitoneal structure, it is not typically removed during RND dissection, as it is an essential immunological organ. Removing the spleen can lead to immunodeficiency and increased susceptibility to infections.
2. **B. Pancreas:** The pancreas is a retroperitoneal structure, but it is not usually removed during RND dissection. The pancreas is a vital organ responsible for producing digestive enzymes and regulating blood glucose levels. Removing the pancreas can lead to severe pancreatic insufficiency and diabetes mellitus.
3. **C. Kidney:** The kidney is a retroperitoneal organ, but it is not typically removed during RND dissection. Kidneys play a crucial role in filtering blood, producing red blood cells, and regulating pH levels. Removing a kidney can lead to severe renal failure and electrolyte imbalances.
4. **D. Omentum:** The omentum is an essential structure involved in protecting, nourishing, and stabilizing the gastrointestinal tract. Removing the omentum during RND dissection can lead to detrimental effects on gastrointestinal function and survival.

**Clinical Pearl:** RND dissection primarily focuses on removing the structures involved in the spread of cancer, while preserving the essential structures necessary for the patient's survival and organ function. Understanding the anatomy and clinical relevance of these structures is crucial for accurate surgical procedures and minimizing complications.