Jorge Lamarche, Alfredo Peguero Rivera, Craig Courville, Mohamed Taha, and Marina Antar-Shultz are Academic Nephrology Attending Physicians at the James A. Haley Veterans' Hospital and Assistant Professors at the University of South Florida Department of Nephrology and Hypertension, all in Tampa, Florida. At the time the article was written Andres Reyes was a Medical Fellow at the University of South Florida. Correspondence: Jorge Lamarche (jorge.lamarche@va.gov)
Author disclosures The authors report no actual or potential conflicts of interest with regard to this article.
Disclaimer The opinions expressed herein are those of the authors and do not necessarily reflect those of Federal Practitioner, Frontline Medical Communications Inc., the U.S. Government, or any of its agencies.
In a patient undergoing peritoneal dialysis with exit-site infection, the presence of > 1 mm radiolucent rim around the subcutaneous catheter after antibiotics has a bad prognosis and prompts catheter removal. This sonographic sign has a positive and negative predictive value for a tunneled infection of 84.6% and 94.1%, respectively.37,38 A risk factor for peritonitis in peritoneal dialysis is air in the peritoneum, which can be seen in one-third of patients. These individuals have 2.4 times more risk of peritonitis compared with patients without pneumoperitoneum. The sensitivity and specificity of sonographic detection of pneumoperitoneum is 94% and 100%, respectively, using the scissor technique.39 Proper training in performing home peritoneal dialysis decreases the incidence of pneumoperitoneum. Although not formally assessed, patient education and change in procedure techniques may decrease the incidence of pneumoperitoneum and peritonitis. The use of prelaparoscopic ultrasonography before insertion of the peritoneal dialysis catheter has detected intra-abdominal adhesions (visceral slide sign) with a sensitivity of 90% to 92%.40
History and physical examination are frequently helpful in the diagnosis of malfunctioning arteriovenous fistulas (AVF) for inflow or outflow disturbances, with sensitivity ranging from 70% to 100% and specificity ranging from 71% to 93% compared with angiography. Frequently, POC limited ultrasound can be helpful for a problematic AVF, either for cannulation or diagnosis. The congruence of duplex sonography with arteriogram is 85% to 96%. Various etiologies of a dysfunctional AVF (pseudo- or true aneurysm, poor development, stenosis, thrombi, or accessory veins) can be observed in the dialysis unit through limited sonography.41-44
After placement of a hemodialysis catheter using real-time ultrasonography, pneumohemothorax can be diagnosed reliably and rapidly. Catheter misplacement outside of the right atrium was detected by thoracic echocardiogram with a sensitivity of 96%, a specificity of 83%, and a positive predictive value of 98%.45,46 Ultimately, ultrasonography may replace chest X-ray in most cases after central vein dialysis catheter placement in the acute care setting.
Postrenal Failure
The sensitivity of ultrasonography to detect dilation to hydronephrosis of the pelvicaliceal system is well established. Sonography is the diagnostic examination of choice in pregnancy and the initial screening test for the nonpregnant patient. Computed tomography is the preferred imaging study in nephroureterolithiasis; however, due to ionizing radiation and cost, ultrasonography is gaining popularity for initial and/or follow-up evaluations. The ureteral jet is a relatively unexplored color and Doppler sonographic methodology that can provide insight into pelvicalyceal peristalsis, potentially yielding evidence of functional obstruction.47-51 Postvoid bladder residual volumes and bladder wall hypertrophy may provide important clues as to the cause(s) of the obstructive uropathy.
Telenephrology
In our institution, sonography is used in the evaluation of IVC, lungs, and kidneys via telemedicine. The probe is handled by trained nurses at the distant site.
The nurses perform and obtain sonographic images under direct supervision provided by a trained attending physician via real-time transmission of the tele-encounter.
Figures 2 to 4 are real-time photos taken to evaluate the IVC (Figure 2), the kidneys (Figure 3), and lungs (Figure 4), respectively, during a clinic video teleconference. The use of “tele-POC sonography” may eliminate unnecessary traveling by patients and lower health care utilization costs while providing real-time assessment of a multitude of clinical issues.
