Renal Colic

Intravenous pyelogram (IVP), spiral CT, and ultrasound are all used in evaluating patients thought to have renal colic. Bedside ultrasound often allows a much more rapid diagnosis and disposition of ED patients than either IVP or spiral CT, and there are situations where the use of contrast material or iodizing radiation is unwise (e.g., pregnancy, renal insufficiency, and volume depletion). False-negative ultrasound results occur, but the sonographic appearance of hydronephrosis in the appropriate clinical setting aids in diagnosis, and negative findings on examination should lead to an alternative diagnosis.

SONOGRAPHIC CONSIDERATIONS A standard 3.5-MHz probe is generally used for renal scanning, but a 5-MHz transducer can be used with better resolution in thin adults and children. The right kidney is best visualized in the anterior to midaxially line over the lower ribs, but a subcostal approach can at times be successful in imaging the kidneys, avoiding the distraction of rib shadows. The left kidney is more difficult to see due to overlying bowel and stomach and the absence of the liver, which acts as an acoustic window, but is perfectly amenable to ED visualization as well. The best initial approach to the left kidney is somewhat more dorsally, in the posterior axillary line over the lower ribs. Occasionally, a posterior thoracic approach is necessary to adequately visualize the kidneys. Deep inspiration lowers the diaphragm and may move the kidneys caudally into a more easily visualized location. To fully evaluate the kidneys for hydronephrosis, both longitudinal and transverse images should be obtained, and both kidneys should be scanned with each examination.

The kidneys are retroperitoneal organs measuring approximately 12 cm in length and 5 cm in width and are divided into two sonographically distinct areas: the renal cortex and the renal sinus. The renal cortex occupies the periphery of the kidney and has an echogenicity similar to that of the liver or spleen. The renal sinus appears as a central echogenic stripe within the kidney and includes the collecting system as well as major vessels of the hilum ( Fig.. ... 295-6). Renal medullary pyramids appear hypoechoic relative to the cortex and are triangular in shape, occurring at the junction of the cortex and the more echogenic renal sinus. When the urine produced in a kidney flows freely into the bladder, there is no appreciable urine within the renal sinus and therefore no significant anechoic space within the hilum. Obstruction of urine outflow from a calculus results in the development of hydronephrosis, which appears as an anechoic fluid collection within the echogenic renal sinus (Fig, 2.95.-Z). Hydronephrosis can be graded from mild, with minimal separation of the sinus echoes, to severe, manifested by extensive separation of the central echoes, with renal parerchymal thinning.

FIG. 295-7. Hydronephrosis of the right kidney with distended renal collecting system (*).

Renal cysts occur commonly and can be confused with hydronephrosis. Renal cysts are thin-walled, round, anechoic structures with distal acoustic enhancement that typically occur in the periphery of the kidney and lack the more echogenic border typical of the collecting system, as seen with hydronephrosis.

The urolith (calculus) causing the obstruction most often lodges at the ureterovesicular junction, the ureteropelvic junction, or the pelvic brim. While stones at the ureterovesicular junction can occasionally be seen sonographically through the bladder window, calculi are usually not identified on ultrasound examinations. One study found that the ureteral calculi were identified on ultrasound in only 19 percent of patients with documented stones, whereas spiral CT and IVP were able to identify 94 and 52 percent, respectively. Hydronephrosis was identified sonographically in 73 percent of the patients with ureteral calculi. 2 In another study, emergency physicians performed bedside renal ultrasound after a 500-mL bolus of normal saline solution in 108 patients suspected of having renal colic. When used in conjunction with the history and a kidney-ureter-bladder film, the emergency physicians were able to diagnose renal colic with a sensitivity of 97 percent. The specificity and accuracy were 59 and 83 percent, respectively.3 It is possible that the fluid loading the patients received prior to the ultrasound studies resulted in a number of the false-positive results that contributed to the low specificity.

Hydronephrosis occurs in over 65 percent of pregnant women, peaking between 24 and 28 weeks of gestation. This is believed to be due to mechanical pressure of the enlarged uterus on the ureters and is usually more pronounced in the right kidney. This condition resolves within several weeks of delivery. False-positive scan results are also seen with overly vigorous hydration or a very full bladder. Peripelvic cysts and extrarenal pelvis are two fairly common conditions that may also cause confusion.

Baby Sleeping

Baby Sleeping

Everything You Need To Know About Baby Sleeping. Your baby is going to be sleeping a lot. During the first few months, your baby will sleep for most of theday. You may not get any real interaction, or reactions other than sleep and crying.

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