Chiefs’ Inquiry Corner – 4/4/22

April 5, 2022

Chief residents of the NYU Langone Internal Medicine Residency give quick-and-easy, evidence-based answers to interesting questions posed by house staff, both in their clinics and on the wards.

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 “Foamy” urine has classically been taught as a sign of proteinuria. It has been suggested that foaming occurs because albumin has a soap-like effect that reduces the surface tension of urine. One study reviewed cases of outpatients presenting over the course of one year, reporting subjective findings of foamy urine. They reviewed the medical records of 1248 patients and identified 72 (6.3%) patients complaining of foamy urine. They reported that 22% percent of patients complaining of foamy urine had overt proteinuria and 31.6% had microalbuminuria or overt proteinuria or both. They concluded that it was reasonable to evaluate patients for signs of proteinuria if they present with this complaint. 

References: Clinical Significance of Subjective Foamy Urine
 The risk of thrombosis varies among the causes of nephrotic syndrome and appears to be highest in patients with membranous nephropathy (where recommendations tend to be most specific). Patients with minimal change disease are also at increased risk of thromboembolism. In addition, the risk of thrombosis is also related to the severity of hypoalbuminemia and tends to occur early in the course of the disease. Recommendations are all based on observational data and there is a lack of randomized trials – so these decisions should be individualized and weighed for each patient. For patients with membranous nephropathy, AC is recommended in: Patients with a low anticoagulation-associated bleeding risk and a serum albumin level <3.0 g/dL AND Patients with a low or intermediate anticoagulation-associated bleeding risk and a serum albumin level <2.0 g/dL. UNC has an online decision tool linked below that takes into account a few factors in weighing risks vs benefits! In patients with a cause of nephrotic syndrome other than membranous nephropathy, AC is recommended in patients with a low or intermediate anticoagulation-associated bleeding risk, and a serum albumin of <2.0 g/dL. The duration of AC is not well-defined, but some recommend continuing until the nephrotic syndrome is in remission or the albumin is >3.0. The experts still generally recommend LMWH or warfarin, with DOACs less understood in this pathology.

References: Prophylactic Anticoagulation in Patients with Membranous Nephropathy
 Pitting describes an indentation that remains in the edematous area after pressure is applied, and it occurs as a result of movement of excess interstitial fluid in response to the pressure (which can occur in conditions like congestive heart failure, though the underlying physiology involves interaction among a number of factors). Non-pitting edema typically occurs in the setting of two major diagnoses, including lymphedema (due to radical mastectomy or lymphatic disease) as well as pretibial myxedema (which occurs as a result of deposition of glycosaminoglycans). Pitting edema can occur in the early stages of lymphedema because of an influx of protein-rich fluid into the interstitium, before fibrosis of the subcutaneous tissue; therefore, its presence should not exclude the diagnosis of lymphedema. 

References: Edema : Diagnosis and Management