Unenhanced CT Scans Research Articles

Distinguishing pelvic phleboliths from distal ureteral stones on routine unenhanced helical CT: is there a radiolucent center?

On radiographs of the abdomen and pelvis, phleboliths often have a characteristic radiolucent center that helps to distinguish them from ureteral stones. On unenhanced CT, the distinction between pelvic phleboliths and distal ureteral stones can be problematic. The objective of this study was to compare the appearance of phleboliths on routine clinical CT studies with their appearance on radiography and to determine if the radiolucent center seen on radiographs is revealed on CT. During a 3-month interval, we identified 50 patients with acute flank pain who underwent both unenhanced CT and abdominal radiography. Patients with a radiograph of the pelvis and an unenhanced CT scan obtained within 1 month of each other were included. CT was performed with a collimation of 5 mm and a pitch of 1. Each phlebolith was examined using soft-tissue and bone settings and was also retrospectively pixel mapped. Seventy-nine (66%) of 120 phleboliths revealed radiolucent centers on abdominal radiography. On CT, 119 (99%) of 120 phleboliths failed to reveal a low-attenuation center on both visual inspection and pixel mapping. Pelvic phleboliths were shown to lack a radiolucent center on routine clinical CT examinations despite their appearance on radiography. A radiolucent center therefore cannot be used to differentiate phleboliths from distal ureteral stones on unenhanced CT in patients with acute flank pain and suspected ureteral obstruction.

Characterization of Adrenal Masses Using Unenhanced CT: An Analysis of the CT Literature

Unenhanced CT scanning can reliably characterize incidentally detected adrenal masses when observers use density measurements of the adrenal gland. However, controversy exists as to the optimal density threshold required to differentiate benign from malignant lesions. This study attempts to establish a consensus by performing a pooled analysis of data found in the CT literature.Ten CT reports were analyzed, from which individual adrenal lesion density measurements were obtained for 495 adrenal lesions (272 benign lesions and 223 malignant lesions). Threshold analysis generated a range of sensitivities and specificities for lesion characterization at different density thresholds.Sensitivity for characterizing a lesion as benign ranged from 47% at a threshold of 2 H to 88% at a threshold of 20 H. Similarly, specificity varied from 100% at a threshold of 2 H to 84% at a threshold of 20 H.The attempt to be absolutely certain that an adrenal lesion is benign may lead to an unacceptably low sensitivity for lesi...

Hyperdense posterior falx in the neonate.

Hyperdense posterior falx and/or torcula on unenhanced CT scans is associated with sagittal sinus thrombosis in adults. However, the validity of this finding in newborns is unknown. A prospective review was performed from September 1995 to November 1996, evaluating head CT scans of infants during their first week of life. Eleven neonatal head CT scans revealed a hyperdense posterior falx, suggestive of sagittal sinus thrombosis. Further imaging (7 ultrasound and 4 magnetic resonance imaging examinations) revealed no evidence of venous thrombosis in 10 of the 11 infants. Predominantly unmyelinated neonatal brain and increased hematocrit of neonatal blood probably contribute to the false impression of hyperdense posterior falx/torcula on neonatal head CT scans.

The pseudo-delta sign is unreliable in differentiating between aneurysmal SAH and sinus thrombosis in unenhanced brain CT

The pseudo-delta sign (PDS) consists of a hyperdense extra-axial triangular image surrounding the low density of the superior sagittal sinus (SSS) in the unenhanced brain CT scan (Fig. 1) [1]. The true delta or empty-delta sign, described by Buonanno et al. in 1978, is only visible on contrast-enhanced films (Fig. 2) [1–4]. The PDS has been described in association with interhemispheric subdural hemorrhage, subarachnoid hemorrhage (SAH) and superior sagittal sinus thrombosis (SSST) [1–5]. The sign has also been encountered with increased attenuation of normal dura surrounding the SSS, diffuse cerebral edema in children and sluggish flow resulting from raised intracranial pressure. Others include calcification of arachnoid granulations and possibly brain death [3,4,6–8]. In an autopsy study of 12 patients with ‘empty triangle sign’, another descriptive term for the PDS, Zilkha et al. found that five of of the patients had SSST. However, they noticed that this sign was not specific for SSST as it was also observed in SAH [3]. The aim of this study was to compare the frequency of PDS in our patients with SAH, SSST as well as in other neurological conditions and to infer its diagnostic accuracy.

Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature.

Unenhanced CT scanning can reliably characterize incidentally detected adrenal masses when observers use density measurements of the adrenal gland. However, controversy exists as to the optimal density threshold required to differentiate benign from malignant lesions. This study attempts to establish a consensus by performing a pooled analysis of data found in the CT literature. Ten CT reports were analyzed, from which individual adrenal lesion density measurements were obtained for 495 adrenal lesions (272 benign lesions and 223 malignant lesions). Threshold analysis generated a range of sensitivities and specificities for lesion characterization at different density thresholds. Sensitivity for characterizing a lesion as benign ranged from 47% at a threshold of 2 H to 88% at a threshold of 20 H. Similarly, specificity varied from 100% at a threshold of 2 H to 84% at a threshold of 20 H. The attempt to be absolutely certain that an adrenal lesion is benign may lead to an unacceptably low sensitivity for lesion characterization. The threshold chosen will depend on the patient population and the cost-benefit approach to patient care.

Estimation of thyroid gland volume by spiral computed tomography.

The objective of this study was to test the accuracy of CT for the estimation of the volume of enlarged thyroid glands. An unenhanced spiral CT scan of neck and upper mediastinum was obtained in 36 patients with an enlarged thyroid gland. By manual segmentation the surface of the thyroid gland on 5-mm-thick slices was calculated; these surfaces were multiplied by the slice interval (10 mm) and summated to obtain the volume of the gland. All patients underwent a total or subtotal thyroidectomy. 1 cm3 of thyroid gland tissue was considered to weigh 1 g. A good correlation was found between the volume estimated by CT and the weight at pathological examination of the resected gland (r = 0.98, p < 0.001), with a mean difference of + 12 % (range: + 57.3 to -13.9 %). The volume calculation is reproducible among different observers (r = 0.99, p < 0.01). Computed tomography allows an easy, reliable and reproducible volume determination of enlarged thyroid glands.

Unenhanced helical CT for suspected acute appendicitis.

The purpose of this study was to determine the diagnostic accuracy of unenhanced helical CT scans in patients with a suspected acute appendicitis. Over a 20-month period, 109 adult patients with suspected acute appendicitis were referred by the emergency department for an unenhanced helical CT scan. Each scan was obtained in a single breath-hold from the T12 vertebral body to the public symphysis using a 5-mm collimation and a pitch of 1.6. No patients were given oral or IV contrast media. The primary CT criteria for diagnosing acute appendicitis was the identification of an appendix with a transverse diameter larger than 6 mm with associated periappendiceal inflammatory changes. The presence of an appendicolith was considered a secondary finding as was isolated periappendiceal inflammation; however, appendicitis was not diagnosed in such patients unless an enlarged appendix was definitely identified. Final diagnoses were established by surgical or clinical follow-up and were compared with the original CT reports. We found 66 true-negatives, 37 true-positives, four false-negatives, and two false-positives that yielded a sensitivity of 90%, a specificity of 97%, a positive predictive value of 95%, a negative predictive value of 95%, and an accuracy of 94%. An alternative diagnosis was established by an unenhanced helical CT scan in 24 patients (22%), which included cecal diverticulitis (seven patients), urinary tract disease (five patients), adnexal pathology (four patients), sigmoid diverticulitis (two patients), small bowel disease (three patients), right lower quadrant tumor (two patients), and an infected dialysis catheter (one patient). Unenhanced thin-section helical CT is an accurate, effective technique for diagnosing acute appendicitis.

Primary malignant lymphoma of the brain

Primary malignant lymphoma of the brain is a disease of unknown etiology, which is increasing in incidence and has an unfavorable prognosis. Despite the lack of specific changes on CT or MRI in most cases, these procedures may typically facilitate the diagnosis: a focal-enhancing mass with subependymal spread on CT or MRI and hyperattenuation on nonenhanced CT are the most reliable features in the diagnosis of primary malignant lymphoma of the brain. Peritumoral edema and mass effect are usually not prominent features. On unenhanced CT scans they usually appear homogeneously isodense to mildly hyperdense relative to the gray matter. On MRI these tumors are slightly hypointense on T1-weighted images and slightly hyperintense on PD- and T2-weighted images relative to the gray matter. On CT and MRI enhancement is usually homogeneous. Contrast-enhanced MRI, with its multiplanar capability, lack of bone-induced artifacts, and high-contrast resolution, is likely to reveal subependymal spread and meningeal involvement that have escaped detection by CT. Because there are no specific features on CT or MRI in most cases, patients who are suspected of having primary malignant lymphoma of the brain should immediately undergo biopsy and, if the diagnosis is confirmed, whole-brain radiation therapy. With early diagnosis and treatment, these patients benefit from radiation therapy.

Effect of hydration status on renal medulla attenuation on unenhanced CT scans.

The purpose of this study was to assess the effect of hydration status on renal medulla attenuation during unenhanced CT. An unenhanced CT scan was obtained in 10 healthy men after 12-18 hr of complete fluid restriction and again after rehydration. CT images were reviewed for the presence and extent of dense renal medulla, defined as greater attenuation than the adjacent cortex. CT findings were correlated with urine-specific gravity and osmolality. Eight of the 10 subjects showed dense renal medulla on a CT scan after dehydration. After rehydration, complete resolution was seen on the CT scan in four of the eight subjects; three of the eight subjects showed a decrease in the extent of dense renal medulla. After rehydration, the eighth subject showed a slight increase in the attenuation of the renal medulla on the CT scan. Dense renal medulla was seen significantly more often on dehydration images (p = .035). Increased renal medulla attenuation on an unenhanced CT scan can be a normal finding related to dehydration.

Timing of parenchymal enhancement on dual-phase dynamic helical CT of the liver: how long does the hepatic arterial phase predominate?

Dual-phase dynamic helical CT is now being used to detect and characterize benign and malignant hypervascular lesions in the liver. The purpose of this study is to define the timing and degree of parenchymal enhancement of normal liver during the hepatic arterial phase. This prospective study included 102 patients with known or suspected hypervascular hepatic lesions who underwent dual-phase helical CT. After unenhanced CT scanning, we injected iopamidol (Isovue 300; Bracco Diagnostics, Princeton, NJ) at 3 ml/sec for 120 ml, then at 2 ml/sec for 55-60 ml. Scan delay for the hepatic arterial phase was 25 sec and for the portal venous phase was 76 sec. Section thickness was 7 mm and pitch was 1:1. Operator-defined regions of interest were obtained from all three phases. Mean unenhanced attenuation of the liver was 51 +/- 12 H. The liver revealed progressive enhancement during the hepatic arterial phase as follows: an increase of 10 H occurred at a mean time of 33 +/- 4 sec, 20 H at 39 +/- 6 sec, 30 H at 44 +/- 8 sec, 40 H at 46 +/- 6 sec, and 50 H at 48 +/- 5 sec. At 20 H and 30 H of enhancement, we found a statistically significant difference (p < .01) for the mean times of men and women. Mean peak enhancement during the portal venous phase was 89 +/- 23 H. Because the hepatic arterial contribution to liver perfusion is approximately 30%, parenchymal enhancement greater than approximately 30% of peak might indicate portal venous predominance. In our study, this percentage corresponded to an increase of approximately 30 H. Therefore, detection of hypervascular lesions in the hepatic arterial phase may be compromised when imaging lasts longer than approximately 44 sec after the initiation of contrast material injection because 44 sec was the mean time for 30 H of enhancement in our series. However, variability between patients was marked, particularly between men and women. Furthermore, the data suggests that the hepatic arterial phase may be relatively brief and that it may be difficult to image properly using current helical CT technology.

Thromboses du sinus longitudinal supérieur chez l'enfant au cours de la première année de vie: aspects cliniques, imagerie etévolution

Thrombosis of the intracranial sinuses and veins may be septic or aseptic, and in the latter case are often due to alteration in hemodynamics. It may also be seen in young babies without known predisposing factors. From 1988 to 1994, 11 children had cerebral venous thrombosis (longitudinal sinus) in the first year of their life. Their ages ranged from two days to 11 months. Transient seizures, lethargy, pseudo tumor cerebri were the first clinical symptoms. The presence of longitudinal sinus thrombosis was suggested by unenhanced CT scan, confirmed by colour doppler flow imaging and magnetic resonance angiography, with absence of blood flow in the longitudinal sinus. Repeated doppler flow imaging showed thrombus resolution within 3 weeks. Thrombosis was associated with predisposing factors in seven cases and appeared idiopathic in the four others. Diagnosis of longitudinal sinus thrombosis can be made more accurately and noninvasively by colour doppler flow and angio-MRI. Treatment with anticoagulants appears unnecessary and dangerous in idiopathic forms.

Unenhanced helical CT of ureteral stones: incidence of associated urinary tract findings.

The objective of this study was to determine the incidence of urinary tract findings associated with ureteral stones on unenhanced helical CT scans of patients with acute renal colic. One hundred forty-one consecutive patients with suspected renal colic were referred by the emergency department for a helical CT scan that was obtained without oral or IV contrast. The CT scans of 54 of these patients were interpreted as positive for ureteral calculi, and these CT scans were reviewed retrospectively. The size and location of each ureteral calculus and of any concurrent urinary tract calculi were recorded. The presence or absence of hydronephrosis, hydroureter, perinephric edema or soft-tissue stranding, and periureteral edema was also noted. We reviewed the original 5-mm axial images from the 54 CT scans. Calculi were present in the proximal, mid, and distal ureter in eight, four, and 14 patients respectively, and at the ureterovesicular junction in 28 patients. Only two patients had more than one ureteral calculus, and none had a contralateral ureteral calculus. Concurrent renal parenchymal and/or nonobstructing calculi in the renal pelvis were seen in five patients with proximal, mid, or distal ureteral stones and in 16 patients with ureterovesicular junction stones. Hydronephrosis was found in 37 patients, hydroureter in 36 patients, and perinephric soft-tissue changes in 35 patients. Periureteral edema could not be evaluated in the 28 patients with ureterovesicular junction calculi because of the adjacent bladder, but periureteral edema was clearly seen immediately adjacent to the ureteral stone in 17 of the other 26 patients. Only two of the 54 patients had no evidence of hydronephrosis, hydroureter, or perinephric soft-tissue changes. In patients with ureteral calculi imaged with unenhanced CT for acute renal colic, associated findings included hydronephrosis, hydroureter, perinephric soft-tissue changes, and periureteral edema. These common findings provided supportive evidence that an acute obstructive process was present.

Detection of intestinal ischemia in patients with acute small-bowel obstruction due to adhesions or hernia: efficacy of CT.

The purpose of this study was to determine whether CT can be used to diagnose ischemia of the small intestine in patients with small-bowel obstruction due to adhesions or hernia. During a 12-month period, 60 patients underwent surgery for complete or high-grade small-bowel obstruction due to adhesions or hernia, and 29 (48%) had evidence of associated intestinal ischemia. All of these patients had been preoperatively diagnosed by CT as having high-grade small-bowel obstruction. At the same time, a prospective determination was made based on the CT as to whether there was any associated intestinal ischemia. All CT scans were performed within 24 hours of the operation. A CT diagnosis of ischemia was based on the presence of two or more of the following signs: bowel-wall thickening, high attenuation of the bowel wall on unenhanced CT scans, mesenteric edema or fluid, asymmetric bowel-wall enhancement on i.v. contrast-enhanced CT scans, pneumatosis, or portal venous gas. Results of the CT examination and surgical findings were then compared. Further evaluation was done with a retrospective multivariate discriminant analysis. Ischemia was prospectively diagnosed on the basis of CT findings in 41 (68%) of the 60 patients. There were no false-negative CT diagnoses (sensitivity, 100%); however, there were 12 CT diagnoses that were false-positive (specificity, 61%). The multivariate analysis corroborated the prospective results by showing high sensitivity (90%) and diminished specificity (50-64%). Bowel-wall thickening and high attenuation of the bowel wall were the most important signs of ischemia on unenhanced CT scans, whereas abnormal bowel-wall enhancement and mesenteric fluid correlated best on enhanced CT examinations. CT is a sensitive but not completely specific preoperative indicator of intestinal ischemia in patients with small-bowel obstruction due to hernias or adhesions.

Unenhanced CT scans in identifying hematomas after blunt abdominal trauma.

Unenhanced CT scans in identifying hematomas after blunt abdominal trauma.

CT diagnosis of early hepatocellular carcinoma: sensitivity, findings, and CT-pathologic correlation.

The purpose of this study was to determine the sensitivity of CT in detecting early hepatocellular carcinoma and to evaluate its CT appearance. An early hepatocellular carcinoma is a nodular lesion with no fibrous capsule composed of well-differentiated tumor histologically. It differs from a small hepatocellular carcinoma, which is an overt tumor that is moderately to poorly differentiated and has a fibrous capsule. Size is not a criterion for distinguishing between early and small hepatocellular carcinomas. Thirty-one patients with 39 histopathologically proved early hepatocellular carcinomas (mean diameter, 1.7 cm) found by sonography, MR imaging, and/or intraoperative sonography were included in a retrospective study. We reviewed unenhanced CT scans of the entire liver in 30 patients (37 lesions) and early and late (35 sec and 5 min after the beginning of injection of contrast material) contrast-enhanced CT scans of the entire liver in all 31 patients (table incremental CT in 21; helical CT in 10; 39 lesions). Eighteen histologically proved small hepatocellular carcinomas (< or = 3 cm; mean diameter, 2.3 cm), present in the same patients, served for comparison. Histopathologically, nine patients had chronic hepatitis, and 22 had cirrhosis. The overall sensitivity of CT in detecting early hepatocellular carcinoma was 56%. These tumors were usually isodense with respect to surrounding liver on unenhanced, early enhanced, and late enhanced CT scans (iso-iso-iso). This pattern was seen in 17 (46%) of 37 lesions; thus, these 17 histologically proved early hepatocellular carcinomas were not detected with CT. An iso-iso-low density pattern was recognized in eight (22%), a low-low-low pattern in seven (19%), and several different patterns in five (13%) of the 37 lesions. Only two (5%) of 39 early hepatocellular carcinomas had a high-density appearance on early enhanced CT scans. In comparison, the most common pattern of small overt hepatocellular carcinomas on CT scans was low-high-low, seen in 17 lesions (94%) detected with CT. When the density of lesions on unenhanced CT scans was compared with the histopathologic appearance of the masses, low-density lesions showed mild to moderate fatty change and isodense lesions showed no or minimal fatty change (p = .006). The sensitivity of CT in detecting early hepatocellular carcinoma is poor (56%). However, the diagnosis of early hepatocellular carcinoma should be considered if CT scans show a small lesion with an iso-low or low-low density enhancement pattern on early and late contrast-enhanced CT scans, respectively, in patients with chronic liver disease.

CT of the lung: patterns of calcification and other high-attenuation abnormalities.

CT is the most sensitive radiologic method for the detection of differences in radiographic density in chest lesions. Areas of high attenuation (visually as opaque as bony structures) in an abnormality on CT scans can be an important clue to the correct diagnosis. The high attenuation is most often caused by calcification, but may also be due to iodine, barium, or radiopaque foreign bodies. This essay illustrates the patterns of high attenuation associated with chest diseases on unenhanced CT scans.

CT of hypervascular hepatic tumors: are unenhanced scans necessary for diagnosis?

In most institutions, a combination of unenhanced and contrast-enhanced CT is used to screen patients for suspected hypervascular hepatic neoplasms. Elimination of the unenhanced examination could save time and expense and reduce the patient's exposure to radiation. We compared unenhanced and incremental bolus dynamic contrast-enhanced CT for detection of hypervascular hepatic neoplasms and evaluated the need for preliminary unenhanced hepatic CT. We prospectively examined 101 consecutive patients with hypervascular primary hepatic malignant tumors or suspected hypervascular metastases. Primary hepatic neoplasms included hepatocellular carcinoma (seven), sarcoma (two), and hemangioendothelioma (one); extrahepatic primary tumors included breast (37) and renal cell (24) carcinoma, melanoma (15), carcinoid (nine), and endocrine and other tumors (six). All patients had both unenhanced and bolus dynamic contrast-enhanced CT with 5-mm collimated sections at 8-mm intervals. For contrast-enhanced CT, 150-180 ml of IV contrast material, a mechanical power injector, and a scanning protocol that allowed completion of liver imaging within 2 min were used. Both unenhanced and contrast-enhanced CT scans were compared for detection and conspicuousness of hepatic lesions. Hepatic lesions were found in 34 patients. In 21 patients, all hepatic lesions seen on unenhanced scans also were apparent on contrast-enhanced scans. However, in 12 (57%) of 21 patients, lesions were more conspicuous and better defined on contrast-enhanced scans. The absolute number of lesions detected with each method of scanning differed in 12 patients. In four patients, the contrast-enhanced scan showed more lesions; in five patients, the unenhanced scan showed more lesions; and in three patients, administration of contrast material obscured some lesions shown on unenhanced scans and made others more conspicuous. If only a contrast-enhanced CT scan had been obtained, the presence of malignant hepatic neoplasm would have been missed in only one case (a patient with a single 2.8-cm metastasis from renal cell carcinoma). Bolus dynamic contrast-enhanced CT alone correctly showed the presence or absence of primary or metastatic hypervascular hepatic tumors in 100 of 101 cases. If the goal of CT examination is detection of hypervascular hepatic lesions, use of contrast-enhanced CT alone may be adequate and the addition of unenhanced scans is not cost-effective.

Abdominal actinomycosis: CT findings in 10 patients.

The purpose of this study was to analyze the CT findings in 10 patients with abdominal actinomycosis to determine the appearance of lesions and the pattern of spread of the disease. We retrospectively reviewed the CT findings in 10 patients with pathologically proved actinomycosis. Involved areas were the pelvis (n = 4), greater omentum (n = 3), liver (n = 2), and kidney (n = 1). Contrast-enhanced (oral and IV) CT scans were available in all patients. Unenhanced CT scans were also available in six patients. CT scans showed mostly solid masses with focal areas of diminished attenuation in seven patients and mostly cystic masses with thickened walls in three. CT findings confirmed the infiltrative nature of the disease, showing its tendency to invade across tissue planes and boundaries. Dense inhomogeneous contrast enhancement in the walls or solid components of masses was seen in eight patients. Minimal lymphadenopathy was seen in only two patients. Although nonspecific, actinomycosis should be included in the differential diagnosis when CT scans show an infiltrative mass with unusual aggressiveness and dense inhomogeneous contrast enhancement, especially in patients with fever, leukocytosis, or long-term use of intrauterine contraceptive devices.

Schistosomiasis japonica of the liver: contrast-enhanced CT findings in 113 patients.

The purpose of this study was to determine the findings on contrast-enhanced CT scans in patients with hepatic schistosomiasis japonica and to determine their pathologic basis. Unenhanced and contrast-enhanced CT scans of 113 patients with histologically proved schistosomiasis were reviewed. Radiologic and pathologic findings were correlated after autopsy in 19 patients. Unenhanced CT scans showed septal calcification in the liver parenchyma in 53 patients (47%) and capsular calcification along the hepatic surface in 29 patients (26%). Twenty-seven patients (24%) had both types of calcification. Fifty-four patients (48%) showed one or more types of enhancement. Septal enhancement (i.e., linear enhancement of hepatic parenchyma looking like septa in the liver) was seen in 52 patients (46%). Forty-seven of the 53 patients who had septal calcification on unenhanced CT scans had septal enhancement on scans obtained after the administration of contrast material. The enhancement was found at sites of septal calcification in 44 patients and at noncalcified sites in 18 (15 had enhancement at both calcified and noncalcified sites). Five of 60 patients who did not have septal calcification on unenhanced CT scans had septal enhancement at noncalcified sites on scans obtained after the administration of contrast material. Amorphous enhancement (i.e., poorly defined and irregularly shaped enhancement) was seen in six patients (5%). Capsular enhancement (i.e., curvilinear enhancement along the hepatic surface) was seen in 12 patients (11%). Histologic studies showed broad fibrous septa at sites of septal enhancement. CT findings in patients with schistosomiasis japonica involving the liver include septal, amorphous, and capsular contrast enhancement. Septal enhancement occurs in broad fibrous septa. CT evidence of septal enhancement may suggest the diagnosis of hepatic schistosomiasis japonica, especially when no calcification is seen on unenhanced CT scans.

CT arterial portography of the abdomen: effect of injecting papaverine into the mesenteric artery on hepatic contrast enhancement.

The purpose of this study was to determine the effect of precontrast injection of papaverine hydrochloride into the superior mesenteric artery on the degree of contrast enhancement of the hepatic parenchyma during CT arterial portography (CTAP, CT with injection of contrast material into the superior mesenteric artery). Twenty-two patients were included in this study. All patients had a baseline unenhanced CT scan and then had CTAP performed with transcatheter injection of 150 ml of nonionic iodinated contrast material (30 g iodine/100 ml) at a rate of 2 ml/sec. Eleven patients received a precontrast injection of 40 mg of papaverine hydrochloride via catheter into the superior mesenteric artery, and 11 patients had CTAP without papaverine hydrochloride. Attenuation of the liver was measured before and after contrast administration in both groups of patients. For each CTAP section, the absolute hepatic enhancement (postcontrast attenuation--precontrast attenuation) and the relative hepatic enhancement ([absolute hepatic enhancement/precontrast attenuation] x 100) were calculated. Also, the mean absolute enhancement and the mean relative enhancement for the entire liver were calculated for each patient. The mean relative enhancement (+/- SD) of hepatic parenchyma was 192 +/- 54% with papaverine hydrochloride and 146 +/- 26% without papaverine hydrochloride. Relative enhancement was significantly higher when papaverine hydrochloride was used (p < .02). The mean absolute enhancement (+/- SD) of hepatic parenchyma was 123 +/- 25 H with papaverine hydrochloride and 91 +/- 19 H without papaverine hydrochloride. Absolute enhancement was significantly higher in patients who had papaverine hydrochloride (p < .01). The results show that precontrast transcatheter infusion of papaverine hydrochloride increases the degree of contrast enhancement of the liver during CTAP.