ADA is an enzyme found in a variety tissues and blood cells including erythrocytes and lymphocytes. Its activity in body fluids is primarily related to the number, maturation and level of stimulation of lymphocytes (1). Although ADA has been used as a diagnostic test for tuberculous meningitis, pericarditis and pleural effusions, caution should be exercised when interpreting its activity in ascitic fluid, particularly in low endemic countries where cirrhosis may not be uncommon. In a study of patients with ascites in the U.S., the overall sensitivity of the ADA for TB peritonitis was 59 % with a specificity of 95% (1). Among cirrhotic patients, however, the sensitivity of ADA was only 30%! False-positive results are occasionally observed in bacterial peritonitis and malignancy-associated ascites (1). Parenthetically, the sensitivity of serum ascites-albumin gradient (SAAG) <1.1 for TB peritonitis is also low (50%) in the setting of chronic liver disease (2).
- Hillebrand DJ, Runyon BA, Yasmineh WG, Rynders GP. Ascitic fluid adenosine deaminase insensitivity in detecting tuberculous peritonitis in the United States. Hepatology 1996;24:1408-1412.
- Shakil AO, Korula J, Kanel GC, Murray NG, Reynolds TB. Diagnostic features of tuberculous peritonitis in the absence and presence of chronic liver disease: a case-control study. Am J Med 1996;100:179-185.
Although measurement of PVR is a common everyday occurrence in hospitalized patients, the threshold of what constitutes an abnormal value is often poorly defined and not standardized. However, most urologists consider volumes of 50 ml to 100 ml to constitute the lower threshold of abnormal PVR (1).
Large PVRs are associated with urinary tract infections, especially in persons at risk (e.g. diabetes, spinal cord injury), while very large PVRs (>300 ml) may be associated with an increased risk of upper urinary tract dilatation and renal insufficiency.
Chronic urinary retention is often defined as a PVR > 300 ml (2).
1. Kelly CE. Evaluation of voiding dysfunction and measurement of bladder volume. Rev Urol 2004;6 (suppl 1):S32-S37. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1472847
2. Kaplan SA, Wein AJ, Staskin DR, Roehrborn CG, Steers WD. Urinary retention and post-void residual urine in men: separating truth from tradition. J Urology 2008;180:47–54. https://www.ncbi.nlm.nih.gov/pubmed/18485378
The association between constipation and urinary retention is well known (1,2). Several mechanisms may explain this relationship, including sharing of the innervations of the internal anal and urinary sphincters via S2-S4 nerve roots, and the presence of impacted stool in the rectum leading to invaginations in the posterior wall of the bladder and urethral obstruction (1,2). Interestingly, in laboratory experiments involving rats, rectal distention with a balloon diminished bladder contractility (2). So, along with many other factors, constipation should routinely be considered a potential cause of acute urinary retention.
1. Selius BA, Subedi R. Urinary retention in adults: diagnosis and initial management. Am Fam Physician 2008;77:643-650.
2. Ariza Traslavina, Del Ciampo LA, Ferraz IS. Acute urinary retention in a pre-school girl with constipation. Rev Paul Pediatr 2015;33:488-492.
The evidence for the accuracy of crackles in CHF is not as robust as often assumed, with wide variations in its sensitivity (13%-70%), specificity (35%-100%), positive predictive value (19%-100%), and negative predictive value (17%-85%) (1).
In a study of patients at high risk for CHF but without valvular heart disease, symptoms of CHF, or comorbid pulmonary disease, the prevalence of baseline crackles in one or both lungs increased with age: 45-64 y , 11%; 65-79 y, 34%; and 80-95 y, 70%. At best, fair or poor negative likelihood ratios (LRs) have been reported for crackles in CHF (3.4, and 0.8, respectively)(2).
The accuracy of crackles in diagnosing pneumonia in patients with cough and fever is not much better: sensitivity 19-67%, specificity 36-94%, and poor positive and negative LRs (1.8 and 0.8, respectively) (2).
So don’t overestimate the accuracy of crackles in CHF or pneumonia, especially if your suspicion for these conditions is high!
- Kataoka H, Matsuno O. Age-related pulmonary crackles (rales) in asymptomatic cardiovascular patients. Ann Fam Med 2008;6:239-245.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2384982/
- McGee S. Auscultation of the lungs. In Evidence-based physical diagnosis (3rd ed.). Elsevier Saunders, Philadelphia, 2012.