USMLE® Step 1 style questions USMLE
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A 32-year-old man comes to the emergency department because of severe left sided flank pain that radiates to his groin. This is his third such episode. A CT is performed and shown below. He is diagnosed with nephrolithiasis, and he is given intravenous hydration and pain management. Which of the following most likely increased this patient's risk of developing nephrolithiasis?
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS
Alright, so renal agenesis—genesis is the origin or formation of something, and the prefix a means not, and renal refers to the kidneys, so renal agenesis is when the kidneys don’t form.
Since there are two kidneys, renal agenesis can refer to just one kidney not developing, called unilateral renal agenesis, or URA, or neither kidney developing, called bilateral renal agenesis, or BRA.
Alright so during fetal development, first off you’ve got this structure called the mesonephric duct which is involved in development of urinary and reproductive organs, and during the 5th week of gestation, a little guy called the ureteric bud starts pushing its way into another structure called the metanephric blastema, and together, these two little embryologic structures go on to develop into a kidney.
At about the 7th week, nephrogenesis, or formation of the kidneys, starts under the influence of that ureteric bud.
By about 20 weeks, the ureteric bud has formed the ureters, renal calyces, collecting ducts, and collecting tubules, while the metanephric blastema develops into the nephron itself, which includes the epithelial cells and the podocytes of Bowman’s capsule.
In the third trimester and throughout infancy, the kidneys continue to grow and mature.
With renal agenesis, the ureteric bud fails to induce development of the metanephric blastema, and so either one or both kidneys don’t develop.
Although not completely known, it’s thought that this is a result of a combination of genetic as well as in utero environmental factors such as toxins and infections.
Newborns with unilateral renal agenesis are usually asymptomatic if the other kidney’s otherwise healthy.
Now that that one kidney’s doing all the filtering, though, over time unilateral renal agenesis can lead to hypertrophy, or growth of the kidney, which later in life can increase the risk of hypertension as well as renal failure.