**Core Concept**
An intravenous urography (IVU) or intravenous pyelogram (IVP) is a radiographic examination used to visualize the urinary tract, specifically the kidneys, ureters, and bladder. It involves the intravenous administration of a contrast agent that is excreted by the kidneys, allowing for imaging of the urinary tract.

**Why the Correct Answer is Right**
The correct answer is **oral cholecystography**. Oral cholecystography involves the ingestion of a contrast agent that is concentrated by the gallbladder, allowing for imaging of the gallbladder and bile ducts. The contrast agent used in oral cholecystography is not excreted by the kidneys, making it a safer option for patients with renal impairment. The contrast agent used in IVU/IVP is excreted by the kidneys, which can be a concern for patients with renal impairment.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the context of the question.
**Option B:** This option is not a correct answer. While oral cholecystography is related to the gastrointestinal tract, it is not the correct answer to this question.
**Option C:** This option is not a correct answer. While IVU/IVP is a type of radiographic examination, it is not taken after oral cholecystography.

**Clinical Pearl / High-Yield Fact**
It's essential to note that oral cholecystography is generally used to visualize the gallbladder and bile ducts, whereas IVU/IVP is used to visualize the kidneys, ureters, and bladder.

**Correct Answer:** D. Oral cholecystography