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A 48-Year-Old with Flank Pain
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A 48-Year-Old with Flank Pain
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Upload Date:
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Language: EN.
Segment:0 .
♪ (music) ♪
CATHY: Hi, welcome to Harrison's Podclass where we discuss important concepts in internal medicine. I'm Cathy Handy.
CHARLIE: And I'm Charlie Wiener,
CHARLIE: and we're coming to you from the Johns Hopkins School of Medicine. ♪ (music) ♪
CHARLIE: Welcome to Episode 35: A 48-Year-Old with Flank Pain." I'll read you the question. A 48-year-old man with diabetes, hyperlipidemia, and atrial fibrillation presents to the emergency department for evaluation of left flank pain, that is radiating to his groin. It's been severe and present for approximately three hours. His medications include metformin, atorvastatin, and warfarin. On examination, he is visibly uncomfortable with a temperature of 37 °C, a heart rate of 105 per minute, a blood pressure of 145 over 95, a respiratory rate of 25 per minute, and a room air saturation of 98%.
CHARLIE: The rest of his physical examination is notable for left flank pain to palpation, but no abdominal organomegaly or focal abdominal tenderness. An electrocardiogram shows sinus tachycardia with nonspecific ST-T wave changes and no suggestion of acute myocardial infarction. His INR is 2.0. His laboratories demonstrate that his renal function is normal, and a urinalysis shows that he has many red blood cells, few white blood cells, no bacteria, and no crystals.
CHARLIE: Cathy, what are your thoughts based on what you've heard so far?
CATHY: So, what we've heard so far is that we have a middle-aged man. He's at risk for vascular disease, given his history of diabetes and hyperlipidemia. But in addition, he is anticoagulated for atrial fibrillation and his INR is at goal. Heard that his EKG doesn't suggest an acute cardiac process, but given his acute severe flank pain, I'm thinking that this may be genitourinary, potentially infectious or an obstruction. We're given a urinalysis, so I'm also thinking that this is likely going to be GU related, but there're no white blood cells or bacteria seen on the urinalysis, so infection is less likely.
CATHY: He does have hematuria, so nephrolithiasis is definitely on the list. And then other things that you have to think about, like vascular or malignant causes of flank pain, that wouldn't usually cause this acute onset of pain, generally.
CHARLIE: Okay, so as you narrow things down, what is the highest on your differential diagnosis?
CATHY: Most likely, given the location, the timing, and the urinalysis, would be nephrolithiasis or pyelonephritis. Less likely, but given his comorbidities, would be an abdominal process, such as appendicitis, cholelithiasis, a perforating duodenal ulcer, pancreatitis or diverticulitis, or even a vascular process such as aortic dissection. And if this was a female patient, I'd also include gynecologic pathologies.
CHARLIE: . Okay, there's a lot of things on the differential here. The question is now going to ask: "Which of the following is the preferred diagnostic study?" And the options are: A. a 24-hour urine collection; B. cystoscopy; C. magnetic resonance imaging, or MRI; D. is a non-contrast CT scan; or E. is an ultrasound.
CATHY: Of the choices listed, and because I'm thinking most about nephrolithiasis, the most sensitive imaging test for that diagnosis is a non-contrast CT. Almost 90% of renal stones in adults are either calcium oxalate or calcium phosphate, and another 6 to 8% are uric acid, but both of which are easily visualized by CT. So, the CT has an excellent chance of visualizing a stone or other process, and avoids the potential toxicity of intravenous contrast, because in CT scans for stones, you should not use contrast.
CHARLIE: And we also know that IV contrast has a greater potential for toxicity in diabetic patients. What about the option of an abdominal ultrasound in this patient?
CATHY: Ultrasound offers the advantage of avoiding radiation and contrast and provides information on hydronephrosis, but it's not as sensitive as CT for suspected nephrolithiasis. Ultrasound testing images only the kidney and possibly the proximal segment of the ureter. Thus most ureteral stones are not detectable by ultrasound. So it's not as good a choice as non-contrast CT for the initial study.
CHARLIE: What about the other listed studies?
CATHY: Urologic intervention, such as cystoscopy, should be postponed, unless there's evidence of a urinary tract infection, a low probability of spontaneous passing. For example, if there is a large stone which typically is considered a stone that's at least 6 mm, or if there's some anatomic abnormality. Or the other reason to consider cystoscopy is if there's intractable pain. A ureteral stent may be placed by cystoscope, but this procedure typically requires general anesthesia. And a stent can be quite uncomfortable, and it can also cause gross hematuria and can increase the risk of a UTI.
CHARLIE: So, what about plain films? In the old days, that's what they would do for stones.
CATHY: Yeah, we didn't mention it here in any of the answer choices, but it's sometimes considered. While it can visualize a calcium-containing stone, it can miss a stone in the ureter or kidney, even if it is radiopaque, and it doesn't provide much information on obstruction. So, these are generally not typically used as adequate testing for nephrolithiasis.
CHARLIE: So, this is a two-part question. The second part of the question asks: "A non-contrast abdominal CT is performed and shown here. Which of the following is the most likely diagnosis?" Cathy, describe what we're seeing on the CT scan.
CATHY: Right. So, this is a CT scan with a coronal view of the abdomen. There is no contrast that's seen on this imaging. The liver, bowel, and the major blood vessels look okay. And we can see both kidneys, and within the patient's left kidney, you see a bright, white, round density that's about the same density as the pelvic bones. And you also see some left-sided hydronephrosis and some perinephric fat stranding on the same side.
CHARLIE: So, the question asks: "Which of the following is the diagnosis?" A. appendicitis; B. nephrolithiasis; C. renal cell carcinoma; D. pyelonephritis; and E. a retroperitoneal hematoma.
CATHY: So, in this imaging you see nephrolithiasis, and given the brightness on CT, it's most likely a calcium-containing stone. As I mentioned earlier, almost 90% of renal stones are this type, and they have a signal density that's similar to bone. The stone is causing some obstruction and early inflammation, and that's why you also see the hydronephrosis and the fat stranding.
CHARLIE: So, since we have a diagnosis of nephrolithiasis, let's quickly review the epidemiology and pathophysiology. Who's at risk?
CATHY: Several conditions predispose to stone formation, including gastrointestinal malabsorption, like Crohn's disease, or gastric bypass surgery, primary hyperparathyroidism, obesity, type 2 diabetes, and distal renal tubular acidosis. A number of other medical conditions are more likely to be present in individuals with a history of nephrolithiasis. So, that would include hypertension, gout, cardiovascular disease, cholelithiasis , reduced bone mineral density, and chronic kidney disease. And if you recall, this patient has diabetes and hypercholesterolemia, so he is a typical at-risk patient.
CHARLIE: What is the pathophysiology of nephrolithiasis?
CATHY: So, recent studies have changed the paradigm for the site of initiation of stone formation. So, we no longer think that they initiate in the renal pelvis. Renal biopsies of stone formers have revealed that calcium phosphate is in the renal interstitium. It's hypothesized that this calcium phosphate deposits at the thin limb of the loop of Henle, and then extends down to the papilla and erodes through the papillary epithelium where it provides a site for deposition of calcium oxalate and calcium phosphate crystals.
CATHY: Now, the majority of calcium oxalate stones grow on calcium phosphate at the tip of the renal papilla, which is also sometimes called Randall's plaque. Tubular plugs of calcium phosphate may be the initiating event in calcium phosphate stone development. So, the process of stone formation may begin years before a clinically detectable stone is identified. And the processes involved in interstitial deposition are under active investigation.
CHARLIE: So, the common theme there is that these stones form on a calcium crystal to start things off. What about the other types of stones?
CATHY: Uric acid stones are the next most common -- at about 8% of stones that are found in patients with hyperuricemia, mostly. Struvite stones are about 1% of stones that we see, and cystine stones are less than 1%. So, both of those are pretty uncommon. Remember that struvite stones are the ones precipitated by bacterial infection such as Proteus, and that's because they promote conversion of urea to ammonium and raise urinary pH. There're also some medications that can cause stones, such as acyclovir, atazanavir, and triamterene.
CHARLIE: Okay, so that's a lot of stuff, but any final comments on management?
CATHY: In the acute setting, you want to do pain management and just make sure that there's adequate hydration. So, for pain management-- because stones can be very painful for patients-- NSAIDs are a good place to start, and are often sufficient for controlling symptoms, and have fewer side effects when compared to opioids. There're also data to support alpha-blockers, for example, tamsulosin to increase the rate of spontaneous stone passage, and most stones will pass spontaneously. More invasive things like surgical interventions are reserved really for larger stones or if there's significant obstruction or an ascending infection.
CHARLIE: Okay, so the teaching point of this case is that in a patient with suspected nephrolithiasis, helical CT without contrast is the initial diagnostic test of choice. The most common stones are calcium-containing, and that comprises, approximately, 90% of cases. And even in the smaller number of patients with uric acid stones, those can also be typically seen on a non-contrast CT. The management is pain control and ensuring adequate urinary flow through hydration. You want to make sure that you're maintaining euvolemia in the patients.
CHARLIE: Alfa-blockers can also be used to help pass along the stones.
CATHY: And to read more about this, you can go to Harrison's chapter on Nephrolithiasis within the Disorders of the Kidney and Urinary Tract. ♪ (music) ♪