Year : 2012 | Volume
: 28 | Issue : 4 | Page : 469--470
Near-infrared spectroscopy for diagnosis of detrusor overactivity: A step towards non-invasive evaluation
Neeraj Kumar Goyal
|How to cite this article:|
Goyal NK. Near-infrared spectroscopy for diagnosis of detrusor overactivity: A step towards non-invasive evaluation.Indian J Urol 2012;28:469-470
|How to cite this URL:|
Goyal NK. Near-infrared spectroscopy for diagnosis of detrusor overactivity: A step towards non-invasive evaluation. Indian J Urol [serial online] 2012 [cited 2022 Jan 27 ];28:469-470
Available from: https://www.indianjurol.com/text.asp?2012/28/4/469/105802
Near-infrared spectroscopy (NIRS) is an optical technology that detects the hemodynamic changes in tissues via noninvasive measurement of changes in the concentration of tissue chromophores such as oxyhemoglobin (O 2 Hb) and deoxyhemoglobin (HHb).  In animal models, significant variations in blood flow to the bladder wall have been revealed during bladder contractions using Doppler ultrasound studies. Similarly, involuntary bladder contractions may cause changes detectable by NIRS. The objective of the present study was to address the accuracy and reproducibility of NIRS to detect the hemodynamic effects of detrusor overactivity (DO).  This study was a prospective cohort study for noninvasive evaluation of DO. A total number of 41 consecutive adult men or women with overactive symptoms were included. Patients with abdominal scars, hematuria, and a history of mixed incontinence were excluded. Anti-muscarinic drugs were stopped three days before urodynamics. Transcutaneous bladder monitoring with NIRS was performed simultaneously with cystometry. An emitter and a sensor were connected to a rubber self-adhesive patch, placed on the abdomen 2 cm above the pubic symphysis across the midline. NIRS data was imported and automatically synchronized (printed) in the urodynamics database. Patient movements, straining, and urine withholding were restricted during the procedure. Surface electromyogram (EMG) monitoring of the abdominal wall muscles (EMG abd ) was used to rule out motion artifacts. Graphs with DO were used as cases and graphs without any DO were used as controls. Graphs contaminated with motion artifacts were excluded.
The cystometry graphs consisted of three curves representing vesical pressure (Pves), abdominal pressure (Pabd), and detrusor pressure (Pdet). NIRS graphs consisted of three curves representing HHb, O 2 Hb, and total hemoglobin (Hbsum). Graphs representing both these tests were separated and presented to three urodynamicists on two different occasions. The urodynamicists marked pressure changes suggestive of DO on the cystometry curves and definite deviations from baseline for NIRS curves.
The study included 17 patients with neurogenic disorders, 21 with benign prostatic enlargement , and three had idiopathic overactive bladder. Urodynamics identified 23 patients with DO, having 47 overactivity episodes. NIRS was highly sensitive in detecting DO episodes: 92% for Hbsum, 82% for O 2 Hb, and 78% for HHb. Similarly, the specificity of NIRS was 86%, 80% and 72% for O 2 Hb, HHb and Hbsum respectively. The overall diagnostic agreement for the three observers was 92% for cystometry graphs. For NIRS, observers agreed on 81% of the HHb, 84% of the O 2 Hb and 81% of the Hbsum curves. The NIRS graphs were rated falsely positive in 18% and false-negative in 15%. No adverse event was noted in any patient related to NIRS.
Overactive bladder syndrome is highly prevalent in the Western culture, negatively affecting the quality of life.  Filling cystometry is the standard urodynamic test to detect DO;  however, it is invasive and may cause patient discomfort and urinary tract infections. Therefore, a noninvasive diagnostic tool that can replace conventional cystometry is recommended, especially for patients who need regular evaluation. Previously, NIRS has been used for bladder outlet obstruction with a good correlation between NIRS and pressure flow parameters.  Cystometry detects the mechanical effect of DO, but NIRS is a unique real-time functional diagnostic modality. There were six false-positive cases (18%), which may be due to DO episodes that were not detected by cystometry. Radley et al.,  showed that conventional cystometry detected DO in only 32 women as compared to 70 on ambulatory urodynamics in a group of 106 women. NIRS failed to identify five of 34 cases with DO as compared to urodynamics. The median change in Pdet at DO was significantly lower in these false-negative cases as compared to the true positive cases (20 vs. 47cm H2O). Therefore, a low-amplitude bladder contraction may be the reason for the false negativity. There are a few limitations noted in the study. The high sensitivity and specificity shown is in case of an optimal study sample (72%), not contaminated with motion artifacts. The situation may be different when applied to a real clinical environment. However, algorithms are being developed for cancellation of motion artifacts which could improve future setups and results. Therefore, NIRS is a potential, noninvasive, diagnostic tool for DO in patients with OAB symptoms. However, its value for clinical use needs to be determined in larger cohorts in the general population.
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