62-year-old (male) with difficulty urinating

by Mohammad Hajighasemi-Ossareh, MD, MBA

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    00:02 A 62 year old caucasian male goes to the emergency room for intense lower abdominal pain associated with inability to urinate.

    00:12 Physical examination shows intense lower abdominal pain.

    00:16 Rectal examination reveals an enlarged, smooth and symmetric prostate.

    00:22 The emergency room team fails to pass a foley catheter through the urethra and the urology team decides to place a suprapubic catheter to drain the urine and relieve the patient's symptoms.

    00:33 An ultrasound shows dilation of the collecting system in both kidneys.

    00:38 Laboratory results reveal an elevated serum creatinine of (1.6 mg/dL) and an estimated glomerular filtration or eGFR of 50 (mL/min/1.73m2) Three weeks after this acute event, the patient visits the urology team for a follow up in clinic, which he claims that time to be having close to normal urination, however it is found that the patient's serum creatinine is 1.5 (mg/dL), persistently elevated.

    01:05 What renal gross findings correlates with this patient's condition? Answer choice (A) - thin cortical rim Answer choice (B) - ureteropelvic junction narrowing Answer choice (C) - enlarged kidneys with bosselated surface Answer choice (D) - pale cortical deposits or answer choice (E) - granular surface Now take a moment to come to the answer by yourself before we go through it together.

    01:38 Okay let's jump in to this question.

    01:40 Let's discuss the question characteristics.

    01:42 Now this is a pathology question.

    01:44 The patient obviously has some kind of a condition in which he has obstruction of urinary outlow, hence pathology and infects the kidneys.

    01:52 So this is Renal-Path.

    01:54 Now this is a 2-step question.

    01:55 We first have to come to a diagnosis then we need to determine what gross macroscopic pathological finding would we expect to be associated with that condition.

    02:06 And the stem is absolutely required to know both the history and also the laboratory findings.

    02:11 Now let's walk through this question together.

    02:13 The first thing we need to do is determine the likely diagnosis.

    02:17 Now this patient presenting with acute urinary obstruction which is secondary to benign prostatic hyperplasia or BPH.

    02:25 Now the presence of an elevated creatinine 3 weeks after the relief of the acute obstruction is actually suggestive of renal damage to the chronic urinary outflow obstruction secondary to the BPH.

    02:39 So before we determine the cause or the etiology of what kind of microscopic finding we would see in the kidneys, let's go through the image to discuss BPH first to help us better understand the condition to then we can better think and figure out why and what type of kidney damage we would expect.

    02:59 Now looking at the image, on the left side we see the image of a normal prostate.

    03:02 the circle there is the bladder, and the urine's going through the bladder and going through the urethra then and the prostate sitting around it.

    03:09 Now on our right side, we see an episode of benign prostatic enlargement or benign prostatic hypertrophy.

    03:15 Now in this case, we actually see again the bladder but urine there it's kind of coming and going back at a nice outflow, and the prostate's enlarged and causing compression of the urethra and inhibiting outflow.

    03:28 And this is what we see in the case of benign prostatic hyperplasia in which the prostate is enlarged and causing compression of the urethra and obstructing urinary outflow.

    03:37 Thus if you were to obstruct your urinary outflow, you will then have obstruction up to the ureters at the kidney and cause a back elevator pressure within the kidney.

    03:47 And thus, going back to our walkthrough this question, the step 2 is to determine the likely macroscopic renal changes associated with BPH.

    03:56 Well think that chronic urinary outflow obstruction like we said, results in urinary tract dilation and also then, renal damage.

    04:05 This is called obstructive nephropathy - vey important to understand.

    04:10 Now, very very high-yield is that obstructive nephropathy is characterized by progressive atrophy of the renal cortex which will then lead to a thin cortical rim of the kidney.

    04:25 Now this has to make sense in your mind, because what's very important to recall here is that it is the renal cortex that contains the nephrons, and thus if you have increased pressure within the middle of the kidney and you push pressure on to the cortex and you thin the cortex out, you're damaging where the nephrons are and essentially you're having that key renal function of urinary production and if you damage that you're gonna have an elevated creatinine level.

    04:52 So in this case, the answer choice is answer choice (A) - thin cortical rim.

    04:58 Now let's discuss some high-yield facts regarding BPH and obstructive nephropathy.

    05:03 Now BPH is common in men after middle age and it presents in around half of men aged about 50 years old.

    05:12 BPH commonly presents with symptoms related to increased frequency of urination, typically a patient who has to keep getting up at night to urinate and difficulty initiating urination or noticing a weak urinary stream.

    05:25 Now BPH can present as acute urinary obstruction with abdominal pain and urinary retention as it did in this question stem.

    05:33 Now let's discuss obstructive nephropathy.

    05:36 Now BPH can result in obstructive nephropathy due to chronic urinary outflow obstruction.

    05:41 Now obstructive nephropathy is characterized by atrophy of the renal cortex.

    05:46 And the typical macroscopic finding of obstructive nephropathy is thinning of the cortical rim of the kidney which is important because the nephrons are located in the cortex and the impairment of the nephrons will cause an impairment of renal function and an elevation in creatinine levels.

    About the Lecture

    The lecture 62-year-old (male) with difficulty urinating by Mohammad Hajighasemi-Ossareh, MD, MBA is from the course Qbank Walkthrough USMLE Step 1 Tutorials.

    Author of lecture 62-year-old (male) with difficulty urinating

     Mohammad Hajighasemi-Ossareh, MD, MBA

    Mohammad Hajighasemi-Ossareh, MD, MBA

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