EUHM Resident Report: Are CT findings valid for prognostication of renal cysts under the Bosniak Classification?

The Bottom Line: CT and MR imaging findings were similar in the majority of cystic renal masses. In some cases, however, MR images may depict additional septa, thickening of the wall and/or septa, or enhancement, which may lead to an upgraded Bosniak cyst classification and can affect case management

Israel, G., Hindman, N., & Bosniak, M. (n.d.). Evaluation of cystic renal masses: Comparison of CT and MR imaging by using the Bosniak classification system. Radiology., 231(2), 365-371.

The Bosniak classification of renal cysts, introduced in 1986, has been used to help evaluate cystic renal masses and decide clinical management. It has been accepted and used by urologists and radiologists as an effective way to assess these lesions, and there has been general interobserver agreement in most instances . Although this classification scheme is based on computed tomographic criteria, the same approach may provide a useful framework for evaluation with magnetic resonance imaging. However, MR imaging may demonstrate some findings that are not depicted at CT, and there may not always be a clear correlation between the findings at MR imaging and those at CT.

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In patients with suspected pyelonephritis, how useful is the finding of costovertebral (CVA) tenderness?

Bottom line:  A finding of CVA tenderness on physical exam does not by itself significantly raise the suspicion of UTI to confirm diagnosis, but can combine with other findings, such as hematuria and dysuria, to guide decision-making.

Summary:  The diagnostic usefulness of CVA tenderness for UTI can be found in the Diagnose app, which incorporates the information from the JAMA Rational Clinical Exam – Bent S, et al.  Does this woman have an acute uncomplicated urinary tract infection? JAMA. 2002;287(20):2701-2710.

Table 2b of this systematic review summarizes the positive likelihood ratio from two studies, a training set and a validation set, that aimed to identify the predictive value of various clinical findings on the diagnosis of uncomplicated UTI.  Uncomplicated refers to a non-pregnant patient with an anatomically and functionally normal urinary tract, and no history of immunosuppression, diabetes, or recent catheterization or urological procedure.  The pooled positive likelihood ratio of a finding of CVA tenderness was 1.7 (95% CI, 1.0-2.2) and the negative LR was o.9 (95% CI, 0.8-1.0).

Try it:  Uncomplicated UTIs can are fairly common among women.  To see how a positive likelihood ratio of 1.7 can change the level of suspicion, check out the Likelihood Ratiop Nomogram at JAMAevidence (click Diagnosis>Likelihood Ratio Nomogram on the menu.)  Use a pre-test probability of 50% and adjust the likelihood ratio indicator to 1.7.

Here is a brief review of likelihood ratios impact on clinical decision-making.

How to differentiate the three types of renal tubular acidosis.

Go to Dynamed section on Renal tubular acidosis (RTA)

Click “Diagnosis” on left menu

Review table:

Testing overview:
-patients with metabolic acidosis due to RTA have low serum bicarbonate concentration, normal anion gap, and negative base excess

-pattern of blood tests and urine studies may help determine specific type of RTA(1, 2, 3, 4)

Test Results in Presence of Metabolic Acidosis (Spontaneously or After Acid Loading)

How do ACE inhibitors act to protect kidney function in the setting of HIV-associated nephropathy?

Bottom line:  ACE inhibitors protect kidney function by decreasing glomerular capillary pressure and by reducing exposure to proteins which could cause proliferation of mesangial cells and matrix.

Summary:  According to Goodman & Gilman’s Pharmacological Basis of Therapeutics [AccessMedicine], ACE inibitors mitigate glomerular injury by decreasing arterial blood pressure and dilating renal efferent arterioles, both of which decrease glomerular capillary pressure.  ACE inhibitors also increase “permeability selectivity of the filtering membrane” which then reduces exposure of the mesangium to proteins, which could stimulate mesangial cell and matrix production.  Reduced intrarenal levels of AngII can also inhibit mesangial cell growth.

For patients with rhabdomyolysis, is bicarbonate effective in preventing damage to the kidneys?

Bottom line:  There is no direct clinical evidence that use of alkalinized fluids is effective at reducing renal damage.

Summary:  The DynaMed article on Rhabdomyolysis (see Treatment>Fluid and Electrolytes) states that use of bicarbonate is controversial lacking directing evidence.  references an exchange about an NEJM paper N Engl J Med 2009; 361:1411-1413) where the author reply reiterates that there is little clinical evidence of effectiveness of bicarbonate.   The authors of the NEJM paper do indicate that some investigators have used bicarbonate solutions in managing rhabdomyolysis, (endpoint was percentage of circulating myoglobin eliminated), but comparative studies cited (in Table 4) did not demonstrate a clinical benefit to use of bicarbonate.

A recent systematic review (Ann Pharmacother. 2013 Jan;47(1):90-105. doi: 10.1345/aph.1R215. Epub 2013 Jan 16.  Prevention of kidney injury following rhabdomyolysis: a systematic review.  Scharman EJ, et al.)
This systematic review corroborates DynaMed and the NEJM paper. It reports several case series and retrospective cohort studies cited in the NEJM paper.  The largest was a retrospective study of a subgroup of 382 patients with rhabdomyolysis and serum creatinine > 5000 U/L. 154 (40%) also received bicarbonate and mannitol in addition to normal saline (NS), compared to 228 (60%) who received NS only. RESULTS: Rates of acute renal failure were 22% (bicarbonate + mannitol) vs 18% (NS only), p =0.27. The two other smaller retrospective cohort studies reported similar findings. See pp. 99-10 of the systematic review for details.

Finally, a recent review (Nature Reviews Nephrology 7, 416-422 (July 2011)) explains (in the Historical Overview section) that the use of bicarbonate was based on experiments demonstrating that myoglobinuria was associated with nephrotoxic effects when the urine was acidic but not when it was alkaline.

What diagnostic testing should be considered in a patient presenting with hypercalcemia?

Figure 9-13. HYPERCALCEMIA: Diagnostic approach to hypercalcemia. In: Pocket Guide to Diagnostic Tests, 6th ed. [AccessMedicine]
Algorithm for workup of patients presenting with hypercalcemia

Read the Diagnosis Section of “Hypercalcemia” in Dynamed

Is there evidence for use of steroids in treating patients with nephrolithiasis?

Bottom line:  One RCT (n=60 ) demonstrated that corticosteroids added to an alpha blocker may reduce the time to expulsion of stones, but the trial did not show any difference in emergency room visits, hospitalizations, analgesic use, number of workdays lost, or quality of life.

SummaryNephrolithiasis.  In:  DynaMed.
In the Treatment>Medications>Medication Expulsion Therapy:
Cites the European Association of Urology recommendations which state that there is insufficient evidence to support use of corticosteroids as an adjunct in patients who are taking alpha blockers.