classified in several ways, ionic/nonionic, monomeric/dimeric, or hyperosmolar/hypo-osmolar.
Side effects, while uncommon, encompass a spectrum, ranging from mild reactions (flushing, tachycardia, and metallic taste in the mouth) to life-threatening effects (hypotension, severe bronchospasm, cardiac arrest).
use of low-osmolality contrast agents is advocated, because these agents have a significantly lower incidence of drug reactions.
After injection of contrast material into a peripheral vein, sequential filming of the kidneys is performed , typically 1–3 minutes postinjection, as well as during contrast excretion into the renal collecting system and ureters (pyelographic phase, typically 3–10 minutes).
Primary indications for this study include hematuria, urinary tract calculi, ureteral obstruction, and evaluation of a suspected congenital anomaly.
Nonenhanced helical CT is rapidly superceding the standard IVU examination in cases of stone disease and ureteral obstruction.
However, IVU remains the procedure of choice for evaluation of suspected uroepithelial neoplasms, such as transitional cell carcinoma, because it more sensitively detects subtle mucosal irregularities.
Retrograde studies of the renal collecting system (retrograde pyelography), ureter (retrograde ureterography), and bladder (cystography)
performed by direct instillation of water-soluble contrast material into the urinary bladder.
These studies are typically performed for evaluation of vesicoureteral reflux, calculi, or tumor.
An AP film from an intravenous urogram taken at 10 minutes in a pt. with a proximal Lt ureteral calculus ( arrow ) and associated left collecting system dilatation. The right collecting system is normal, and the right ureter ( arrowheads ),bladder are seen.
Endoluminal sonography is used to image structures beyond the lumen of the hollow viscus.
It is accurate in local staging of cancer and in detecting small lesions that may not be visualized with other imaging modalities.
GI applications include quantification of the size and wall thickness of esophageal carcinoma or varices. Eg. Upper GI endoscopy and colonoscopy.
Transrectal USG is performed for evaluation of the prostate.
Genitourinary (GU) applications include examination of the severity and length of ureteral strictures, diagnosis of upper tract neoplasms and urethral diverticula, identification of submucosal calculi.
d. The uterus, adnexa, and routine fetal examinations by using a transvaginal probe in the presence of an empty bladder.
Sonohysterography, an ultrasound-guided procedure, requires instillation of a sterile saline solution into the uterine cavity following cannulation for evaluation of endometrial masses or other abnormalities.
f. Transesophageal echocardiography is used for evaluating cardiovascular abnormalities after placement of a probe into the esophagus.
g. Three-dimensional ultrasound (3D-US) is widely used in obstetrics and vascular imaging.
3D-US is used to quantify the volume of organs and pathology.
It has been used predominantly in obstetrics for studying normal embryonic and/or fetal development and
for detecting specific congenital anomalies in a fetus at risk given a known family history.
Nuclear medicine studies are performed by administering a radiopharmaceutical to the patient and subsequently recording its distribution in the body over a defined period of time.
In general, these studies are very sensitive, but relatively nonspecific, in the detection of pathophysiology.
Correlation with pertinent clinical history, physical findings, laboratory data, and other diagnostic imaging procedures is, therefore, essential to render an accurate interpretation and for maximizing clinical benefits to both the patient and ordering physician.
cardiac studies for evaluation of myocardial perfusion and/or ventricular function;
skeletal studies for detection of early bone metastases and primary bone neoplasms;
renograms and renal scans for assessment of renal function and morphologic defects (e.g., pyelonephritis);
ventilation–perfusion studies for identification of suspected pulmonary emboli; and
PET studies for tumor diagnosis and staging (e.g., lung, colorectal, breast, lymphoma, melanoma), as well as for evaluation of neurodegenerative disorders (dementia), brain tumor recurrence, and myocardial viability.
e. gastrointestinal bleeding studies for detection and localization of small bleeds,
f. lymphoscintigraphy to identify sentinel lymph nodes for surgery, and
g. parathyroid scans to identify adenomas and hyperplasia.
A 99m Tc-MDP bone scan in the anterior and posterior projections demonstrates multiple foci of increased radiopharmaceutical accumulation (spine, ribs, pelvis, and left clavicle) with the typical appearance of bone metastases.