99Tcm-nanocolloid imaging in inflammatory bowel disease

We have used 99Tcm-labelled nanocolloid in an attempt to locate areas of inflamed bowel wall or abscesses in five patients with ulcerative colitis and nine with Crohn's disease. The scintigraphic findings were evaluated by comparison with those of recent barium studies and, in three patients, with surgical findings at laparotomy. It proved difficult to localize segments of inflamed bowel accurately with 99Tcm-nanocolloid because of the accumulation of radioactivity in the gut lumen, especially 2 or more hours after injection. However, there was little uptake of the labelled nanocolloid by areas of inflamed gut wall in the period before 2 h. When 99Tcm-nanocolloid scans were compared with 111In-WBC scans in eight patients who had both investigations, 99Tcm-nanocolloid scintigraphy was considerably less sensitive than 111In-WBC scintigraphy. One abscess was located correctly; the other was obscured by nearby bladder and bone marrow radioactivity. We conclude that 99Tcm-nanocolloid scanning is neither sensitive nor reliable enough for assessing the location of inflamed bowel wall or the presence of abscess in patients with inflammatory bowel disease.     

The single late 99Tcm granulocyte antibody scan in inflammatory diseases.

Immunoscintigraphy using 555-740 MBq 99Tcm-labelled monoclonal antigranulocyte antibodies (IgG1 against NCA-95) (BW250/183) was performed in 56 patients. In 32 of them inflammatory or infectious lesions were proven or excluded histologically. Gamma camera scans were performed 4 to 6 and 20 h postinjection (p.i.). Eight of 14 infectious or inflammatory lesions could be detected in the early scan (4-6 h p.i.). Sensitivity, specificity and diagnostic accuracy of the early scan were 57, 89 and 75%. Sensitivity, specificity and diagnostic accuracy in 19 patients with bone or prosthetic bone infections (87, 81 and 84%, respectively) were lower than in patients with abdominal or soft tissue infections (100%). The overall sensitivity, specificity and diagnostic accuracy of the 20 h scan was 86, 89 and 88%, respectively. It is concluded that the high diagnostic accuracy of immunoscintigraphy justifies a broader application of the scan in the diagnosis of infectious diseases. It is recommended that only late scans (20 h p.i.) are necessary.     

Technetium-99m HM-PAO-labeled leukocytes in detection of inflammatory lesions: comparison with gallium-67 citrate

Forty-three patients with suspected benign, inflammatory, or infectious diseases were imaged with [99mTc]HM-PAO-labeled leukocytes and [67Ga]citrate. Technetium-99m leukocytes showed 22 true-positive, no false-positive, 19 true-negative, and two false-negative findings and [67Ga]citrate 23, 7, 12 and 1, respectively. The sensitivity, specificity, and accuracy values with 99mTc leukocytes were 92%, 100%, and 95%, and with [67Ga]citrate 96%, 63%, and 81%. Technetium-99m leukocyte scintigraphy has a promising future in comparison with [67Ga]citrate because of the ready availability of [99mTc]HM-PAO, the good image quality, more rapid results (within few hours), and the lower radiation exposure to the patient with 99mTc leukocytes. The usefulness of 99mTc leukocytes in chronic osteomyelitis needs further evaluation.     

Clinical application of Tc-99m HMPAO labeled leukocyte imaging in inflammatory disease]

A radionuclide imaging with Tc-99m HMPAO labeled leukocyte was performed in order to determine its clinical usefulness in inflammatory disease. The mixed leukocyte isolated from 40 ml of whole blood containing 5 ml of acid citrate dextrose A and 7 ml of 6% hydroxyethyl starch was incubated with 370 MBq (10 mCi) of Tc-99m HMPAO at 37 degrees C for 30 minutes. Because the labeling efficiency of Tc-99m HMPAO labeled leukocyte was 60.2 +/- 6.3%, the procedure of washing Tc-99m, leukocyte with 5 ml of physiological saline was necessary before intravenous injection, in order to remove the unlabeled Tc-99m HMPAO. The recoveries of Tc-99m leukocyte in the blood after intravenous injection were 41.1 +/- 6.7% at 5 minutes, 33.4 +/- 2.1% at 30 minutes, and 27.2 +/- 3.4% at 2 hours after injection. Moreover, the labeled leukocyte was not stained with trypan blue. Therefore, the biological activity of the Tc-99m leukocyte was maintained as that of In-111 oxine labeled leukocyte. In the 39 patients with clinical suspicion of inflammatory disease including 15 patients with acute and chronic infectious disease where both Tc-99m leukocyte and Ga-67 citrate imagings were performed, the sensitivity, specificity and accuracy for infectious disease were 47%, 100% and 79% with Tc-99m leukocyte, and 67%, 79% and 74% with Ga-67 citrate. These results suggest that Tc-99m HMPAO labeled leukocyte imaging is promising for evaluating inflammatory disease because of the much higher specificity, the ready availability of Tc-99m HMPAO, the good image quality, and the lower radiation dose to the patient.     

Inability of 99mTc-ciprofloxacin scintigraphy to discriminate between septic and sterile osteoarticular diseases.

Ciprofloxacin labeled with (99m)Tc specifically binds to various bacteria. Thus, it potentially constitutes a specific marker allowing discrimination between septic arthritis/osteomyelitis and aseptic osteoarticular diseases. The aim of this prospective study was to evaluate such properties in patients with skeletal diseases. METHODS: We prospectively investigated 2 groups of patients: patients with suspected osteoarticular infections (G1, n = 16) and a control group of patients with a presentation of osteoarticular diseases and no sign suggestive of infection (G2, n = 11). All had clinical, biologic, and radiologic evaluations and had 1-, 4-, and 24-h images from (99m)Tc-ciprofloxacin scintigraphy (370 MBq) before planned biopsy or surgery. For 23 patients, the scintigraphic results were compared with histologic and bacteriologic analyses of biopsy tissue samples; for 4 patients, the scintigraphic results were compared with the findings from 23 +/- 5 mo of follow-up. RESULTS: In G1, (99m)Tc-ciprofloxacin findings were true-positive in all 11 infected sites, true-negative in 2 cases, and false-positive in 3. In G2, (99m)Tc-ciprofloxacin was true-negative in 4 cases and false-positive in 7. Neither the location of (99m)Tc-ciprofloxacin activity nor its intensity or kinetics between 1, 4, and 24 h allowed discrimination between infection and aseptic diseases (sterile loosened joint replacement, pseudoarthrosis, or arthrosis). Sensitivity, specificity, and accuracy were 100%, 37.5%, and 63%. CONCLUSION: (99m)Tc-Ciprofloxacin scintigraphy showed good sensitivity and a high negative predictive value for the detection of bone and joint infection, but it did not discriminate between infected and aseptic osteoarticular diseases in symptomatic patients referred for surgery.     

99mTc-HMPAO labelled leucocyte scintigraphy in the diagnosis of pelvic inflammatory disease

BACKGROUND: Scintigraphy using leucocytes labelled with 99mTc hexamethylpropyleneamine oxime (99mTc-HMPAO) is widely used for the localization of inflammatory foci and abscesses in cases of acute pelvic inflammatory disease, which is one of the serious health problems of women of child-bearing age. Early diagnosis and effective management of this condition can preserve fertility and prevent serious complications, such as peritonitis and sepsis. AIM: To evaluate the importance of scintigraphy using 99mTc-HMPAO labelled leucocytes in the early diagnosis of patients with pelvic inflammatory disease. METHODS: Fifteen women (mean age 29.2+/-8 years, range 25-46 years) with suspicion of pyogenic pelvic inflammatory disease based on gynaecological examinations, clinical findings and blood tests were included in this study. The patients received 555 MBq 99mTc-HMPAO labelled leucocytes, by injection, and were scanned by scintigraphy 0.5-1, 3 and 24 h later in the anterior abdominal projection. Ten of the patients were then evaluated by abdominal or transvaginal ultrasonography, four by computed tomography and two by both ultrasound and computed tomography. The final diagnosis was made by surgical intervention. RESULTS: Scintigraphy detected pelvic inflammatory disease in five of the patients. In three of them the disease was apparent on the scans taken at 0.5-1 h, and in the other two it was apparent at 3 h. There were no false negative results, and one false positive result. The scan accurately reflected the absence of pelvic inflammatory disease in nine patients showing non-pathological tracer uptake in the lower abdominal region. CONCLUSION: We showed that scintigraphy with 99mTc-HMPAO labelled leucocytes had a sensitivity of 100%, specificity of 90%, overall accuracy of 93%, positive predictive value of 83%, and negative predictive value of 100%. Therefore, we conclude that 99mTc-HMPAO labelled leucocyte scans provide a rapid and highly accurate method for diagnosing pelvic inflammatory disease in women of child-bearing age. This adds an important contribution to the diagnosis of infection and helps determine further operative or conservative treatment.     

99mTc-DTPA-HSA lymphoscintigraphy in lymphedema of the lower extremities: diagnostic significance of dynamic study and muscular exercise

The efficacy of lymphoscintigraphy was evaluated in 25 cases to clarify the diagnostic significance of dynamic study and muscular exercise in the diagnosis of lymphedema. 99mTc-diethylene triamine pentaacetic acid-human serum albumin (DTPA-HSA) was injected subcutaneously, and dynamic imaging was performed in 18 cases. Thirteen patients were asked to walk for 3 minutes. Qualitative evaluation of static images had sensitivity of 90% and specificity of 97%. Diagnostic criteria including qualitative evaluation of dynamic images were less specific (sensitivity 95%, specificity 76%). Interpretation of static images obtained at one hour after injection in the patients without muscular exercise had sensitivity of 89% and specificity of 67%, whereas sensitivity was 92% and specificity was 100% in the patients with muscular exercise. Lympho-scintigraphy was reliable in diagnosis of lymphedema. Dynamic study was limited usefulness because of some false-positive cases. Muscular exercise accelerated migration of the tracer in normal extremities, and improved positive predictive value.     

Inflammation: imaging with Tc-99m HMPAO-labeled leukocytes

Leukocytes labeled with technetium-99m hexamethylpropyleneamine oxime (HMPAO) were used in 100 patients: 32 with suspected inflammatory bowel disease, 17 with fever of unknown origin, 21 with suspected abdominal sepsis, 20 with suspected bone sepsis, seven with bronchiectasis, and three with recent myocardial infarction. The distribution of activity in patients subsequently shown not to have inflammatory bowel disease was similar to that previously described for indium-111-labeled leukocytes. However, in this study, activity was also seen in the kidneys and bladder and occasionally the gallbladder on both early (1-3 hours) and late (24 hours) views, and in the colon in late views. Migration of Tc-99m-labeled granulocytes was seen in inflammatory disease as early as 30 minutes after injection, while normal bowel activity was not seen before 4 hours. The sensitivity of Tc99m-labeled leukocytes in the detection of inflammation was 100%, the specificity was 95%.     

Technetium-99m-labeled anti-granulocyte antibodies in suspected bone infections.

The introduction of 99mTc-labeled anti-granulocyte antibodies seemed to provide advantages in comparison with formerly used in vitro methods to label autologous white blood cells for inflammation imaging. For this reason, we have undertaken a study to evaluate the clinical significance of this method. Thirty unselected patients with suspected bone infections were studied prospectively using the monoclonal 99mTc-labeled anti-granulocyte antibody. Twenty patients were referred with suspected infections of the peripheral bones (Group I), as well as 10 patients with suspected infections of the spine (Group II). Planar whole-body scans were performed 4 hr and 20 to 24 hr after administration of 500 MBq of the labeled antibody. Scans were considered positive for a bacterial (septic) infection when a focally increased antibody accumulation occurred. All scans were evaluated in blinded fashion by two experienced readers. Of the 20 studies from Group I patients, four false-positive scintigraphic findings were observed, and one false-negative, resulting in a specificity of only 64% and a sensitivity of 89%. In Group II (10 studies), five scans were true-negative, and five false-negative. For both groups, the specificity of the scintigraphic method was quite low (75%), and the sensitivity was also relatively low (57%). The results of this study demonstrate that in an unselected patient population in whom the diagnosis is not known, scintigraphy with 99mTc-anti-granulocyte antibodies is not a reliable method for detecting septic inflammatory lesions: In addition, use of this method excludes septic lesions with only a moderate likelihood (83% negative predictive value).     

The comparison of dual phase Tc-99m MIBI and Tc-99m MDP scintimammography in the evaluation of breast masses: Preliminary report

The aim of this prospective study was to determine the diagnostic value of Tc-99m MDP scintimammography (SMG) for the detection of breast cancer in patients with breast masses and to compare the results with Tc-99m MIBI scintimammography. Twenty patients, categorized as suspicious, positive or benign for breast cancer according to the mammographic findings were included in the study. Dual phase Tc-99m MIBI and Tc-99m MDP SMG were performed in the prone lateral position within 5 days of each other. Although early and late Tc-99m MIBI SMG showed equal (90.4%) sensitivity, the specificity of late Tc-99m MIBI (87.5%) was found superior to early (62.5%) imaging. The overall sensitivity and specificity of early Tc-99m MDP SMG were 71.4% and 62.5%, respectively. Although late Tc-99m MDP imaging showed 100% specificity, its sensitivity was only 23.8%. In the patients with palpable masses, both early Tc-99m MDP and Tc-99m MIBI showed equal sensitivity (100%), but the sensitivity of early Tc-99m MIBI (37.5%) was found slightly higher than Tc-99m MDP (25.0%) for nonpalpable breast lesions. The sensitivity of Tc-99m MIBI and Tc-99m MDP SMG in detecting metastatic axillary involvement was 66.6% and 50%, respectively. High sensitivity and specificity together with its low cost, easy availability and the possibility of detecting bone metastases seems to make Tc-99m MDP a contributive agent in the evaluation of breast lesions as an alternative to Tc-99m MIBI.     

Bone marrow scintigraphy in the diagnosis of post-traumatic avascular necrosis of bone

A series of 19 patients, who were clinically suspected of developing avascular necrosis of bone following fracture, were entered into a pilot study comparing the use of bone marrow scintigraphy with conventional skeletal scintigraphy. Two-phase bone scintigraphy, using 600 MBq of 99Tcm-HMDP, and perfusion and late-phase nanocolloid scintigraphy, using 370 MBq of 99Tcm-nanocolloid, were performed on each patient. In both methods, photon deficiency at the site of interest was taken to indicate avascularity. The perfusion phase of both methods was found to be unhelpful. Agreement between methods was obtained in 18 patients (95%). Six patients had abnormal nanocolloid scans, one of which was normal on the conventional bone scintigram. The remaining 13 patients had no evidence to suggest avascularity in either method. Three of the patients with abnormal scans have had hip replacement surgery following which avascularity of the femoral head was confirmed. 99Tcm-nanocolloid scintigraphy is thus shown to be a very sensitive method of demonstrating avascularity of bone following trauma.     

Osteomyelitis

The use of 111In-labelled granulocyte scintigraphy is recognized as a reliable method for detecting osteomyelitis and has similar sensitivity and significantly increased specificity compared to bone scintigraphy and 67Ga studies. Recent published work using pure granulocytes labelled with 111In tropolonate to detect osteomyelitis resulted in sensitivity of 100% and specificity of 92%. 99Tcm as an alternative granulocyte label offers advantages of convenience, lower radiation dose and higher image resolution. We have scanned 20 patients with suspected osteomyelitis using autologous granulocytes labelled with 99Tcm hexamethylpropyleneamineoxime (HMPAO), 12 of whom had prosthetic joints. The scan results were correlated with clinical, radiographic, microbiological and histological findings. Sensitivity was 100% and specificity was 93% which compares favourably with results obtained using 111In-labelled granulocytes. We believe that labelled granulocyte scintigraphy is a useful investigation in the diagnosis of osteomyelitis and that 99Tcm HMPAO appears to be at least as useful as 111In as the labelling agent.     

Synthesis and comparison of 99mTc-enrofloxacin and 99mTc-ciprofloxacin.

The use of (99m)Tc-ciprofloxacin as a tracer for infection and inflammation has been examined and discussed in the literature extensively. Its alleged ability to discriminate between sterile inflammation and bacterial versus nonbacterial infections has led to an intense debate. Other labeled fluoroquinolones might offer better characteristics or may add to a better understanding of the working mechanism of (99m)Tc-ciprofloxacin. The rationale of this work was to determine possible differences in the use of 2 labeled quinolones--that is, (99m)Tc-ciprofloxacin and (99m)Tc-enrofloxacin--as tracers for infection and inflammation in animals. METHODS: Ciprofloxacin and enrofloxacin were labeled with (99m)Tc and characterized. The stability of both preparations was evaluated in serum and in the presence of an excess of cysteine. In vitro binding studies were performed to determine the interaction of the labeled quinolones with bacteria and other cells. Rats with sterile and infectious intramuscular lesions were used to study the scintigraphic properties of the 2 compounds. To assess the specificity of binding to living bacteria, infectious intramuscular lesions of heat-killed Staphylococcus aureus and Candida albicans were used as controls. Imaging was performed with a gamma-camera at 0, 3, 5, and 22 h after injection. RESULTS: The radiochemical purity of both radiolabeled fluoroquinolones exceeded 95% as determined by instant thin-layer chromatography. Both compounds were moderately stable in serum. Binding assays did not show any saturable binding to S. aureus, heat-killed S. aureus, as well as C. albicans. None of the tracers showed specific binding to bacteria. Scintigraphy showed uptake in the infectious lesion at 1 h after injection, which washed out during the next 4 h. Abscess-to-muscle ratios for both preparations were not significantly different for the various infectious or inflammatory lesions studied and did not exceed an average of 4.25 +/- 0.62. CONCLUSION: The study demonstrated that (99m)Tc-ciprofloxacin and (99m)Tc-enrofloxacin do not show preferential binding to living bacteria. In vivo (99m)Tc-enrofloxacin has similar characteristics as (99m)Tc-ciprofloxacin except for differences in uptake in a few normal tissues.     

Diagnosis of pyogenic pelvic inflammatory diseases by 99mTc-HMPAO leucocyte scintigraphy

Pelvic inflammatory disease (PID) is one of the major health problems of women of child-bearing age. Among the most serious complications of PID is the formation of a tubo-ovarian abscess (TOA). Early diagnosis of this condition may prevent serious surgical complications such as peritonitis and sepsis, which may be fatal. The purpose of this study was to investigate the efficacy of technetium-99m hexamethylpropylene amine oxime (HMPAO) leucocyte scintigraphy in the diagnosis of TOA. Twenty women with high clinical suspicion of TOA underwent 99mTc-HMPAO leucocyte scintigraphy. The labelling of leucocytes with 99mTc-HMPAO was performed according to a standard protocol. Scans were obtained at 1, 3 and 24 h following the injection of the labelled leucocytes. In eight cases the early and/or late scan was positive, in 11 cases it was negative, and in one case of ovarian cyst torsion, confirmed by laparoscopy, it showed slight uptake in the capsule of the cyst (false-positive). The sensitivity of 99mTc-HMPAO leucocyte scintigraphy was 100%, specificity 91.6%, positive predictive value 89%, negative predictive value 100% and overall accuracy 95%. It is concluded that leucocyte scintigraphy is a non-invasive, safe, physiological and accurate procedure for the diagnosis of TOA. The 24-h scan is crucial, since in some cases the abscess was not clearly visualized on the early scan. Leucocyte scintigraphy may reduce the need for CT, diagnostic laparoscopy and unnecessary invasive surgical procedures.     

99mTc-stannous colloid white cell scintigraphy in childhood inflammatory bowel disease.

99mTc-Labeled white cell scintigraphy (WCS) has been used for the investigation of inflammatory bowel disease (IBD) in adults, but data on children are limited. The most common agent used is (99m) Tc-hexamethylpropyleneamine oxime (HMPAO); however, this agent has limitations. In a retrospective study, we assessed the use of (99m)Tc-stannous colloid WCS for the initial evaluation of children with suspected IBD. METHODS: Diagnostic, endoscopic, and contrast radiography results were retrospectively collected from the medical records. Two experienced nuclear physicians unaware of the patient data interpreted the WCS results, with agreement reached by consensus. Statistical analysis was performed on the ability of WCS to detect active disease and localize it topographically and on a comparison of diagnostic methods, using a combination of clinical features and endoscopy as the reference standard. RESULTS: Between 1996 and 1999, 64 patients (35 male and 29 female; mean age, 12.5 y; age range, 2-19 y) had WCS performed, with IBD subsequently diagnosed in 34 patients. (99m)Tc-Stannous colloid WCS had an 88% sensitivity, 90% specificity, and 8.8 likelihood ratio for initial investigation of IBD. Agreement was poor for topographic localization of disease. Small-bowel series had a 75% sensitivity, 50% specificity, and 1.5 likelihood ratio for detecting endoscopic disease of the terminal ileum and proximal colon. CONCLUSION: Our results confirm that WCS is a useful imaging technique for the initial evaluation of patients with suspected IBD. (99m)Tc-Stannous colloid had results at least comparable to those of other WCS agents, and in children, (99m)Tc-stannous colloid WCS should be preferred in view of lower cost, shorter preparation time, and the smaller blood volumes required.     

Evaluation of peritoneovenous shunt patency by intraperitoneal Tc-99m macroaggregated albumin: clinical experience

The clinical utility of peritoneovenous shunt patency studies using intraperitoneal Tc-99m macroaggregated albumin was studied. The patency of a peritoneovenous shunt can be reliably determined using the intraperitoneal injection of Tc-99m macroaggregated albumin with the appearance of lung activity as an indicator of patency. In an evaluation of 66 cases of clinically suspected peritoneovenous shunt obstruction, using the appearance of lung activity as the sole criterion of patency, this technique was shown to have a sensitivity of 100%, specificity of 92.2%, and accuracy of 98.5%. Visualization of efferent shunt tubing was variable and not a reliable criterion of shunt patency. This technique should be considered when peritoneovenous shunt patency is questioned.     

Clinical evaluation of 99Tcm-MIBI SPECT in the assessment of coronary artery disease.

To evaluate the clinical efficacy of 99Tcm-MIBI myocardial tomography for detecting coronary artery disease (CAD) 115 consecutive patients who underwent both 99Tcm-MIBI single photon emission computed tomography (SPECT) and coronary arteriography were studied. Thirty-three patients without and 82 with significant coronary artery disease were documented by coronary arteriography. The overall sensitivity and specificity of 99Tcm-MIBI SPECT for detecting coronary artery disease were 96 and 87.9%, respectively. The sensitivity for identifying patients with CAD without myocardial infarction was 88%. The sensitivity of 99Tcm-MIBI SPECT for detecting individual coronary artery lesions was 86% for left anterior descending artery (LAD), 69% for left circumflex artery (Lcx) and 86% for right coronary artery (RCA), lesions respectively. In conclusion, 99Tcm-MIBI SPECT provides a reliable method for detecting CAD.     

~(99m)Tc-MIBI肝胆动态显像对先天性胆道闭锁的诊断价值

目的评价99m锝-甲氧基异丁基异腈(99mTc-MIBI)肝胆动态显像在先天性胆道闭锁(BA)诊断中的临床应用价值。方法 52例患儿静脉注射99mTc-MIBI后,用SPECT进行肝胆动态显像,并经手术病理和临床随访结果证实。结果在17例最终诊断为BA的患儿中,99mTc-MIBI肝胆显像全部检出,灵敏度、特异度和准确性分别为100%、80.9%、92.3%。结论 99mTc-MIBI肝胆动态显像是无创、安全、有效的检查方法,对于BA的诊断,有较高的临床应用价值。     

Diagnosis of upper-abdominal infections by In-111 labeled leukocytes with Tc-99m colloid subtraction technique

In 65 patients suspected of upper-abdominal inflammatory disease, indium-111 leukocyte scintigraphy was combined with a Tc-99m(Sn)colloid scan by computer-assisted subtraction. In 84% of these cases, a definite diagnosis would not have been possible without this method of subtraction. Accuracy was found to be 80%, sensitivity 93%, and specificity 59%. False-positive results were due either to noninfectious inflammatory lesions with accumulation of leukocytes or to some pitfalls in the subtraction technique itself.     

Individual renal function based on 99mTc dimercaptosuccinic acid uptake corrected for renal size

BACKGROUND: Decreased relative 99mTc dimercaptosuccinic acid (99mTc-DMSA) uptake can be a consequence of abnormal kidney size, associated with normal or impaired function. When there is a small kidney, relative 99mTc-DMSA uptake is decreased, and it is sometimes difficult to distinguish a small, normal kidney from a hypofunctioning kidney. Here, relative renal function was studied by quantifying the relative 99mTc-DMSA uptake corrected for renal size (RCU). METHODS: Five hundred and fifty-five consecutive patients (184 adults) aged 1 month to 82 years (mean, 14.8 years) underwent a 99mTc-DMSA study for various renal diseases. Results were compared with the relative 99mTc-DMSA uptake without size correction (RUU). Visual evaluation of images was also performed. RESULTS: In 288 patients (52%) the relative 99mTc-DMSA uptake was normal, either uncorrected or corrected, for renal size; in 184 (33%) it was abnormal by both quantification methods; and in 83 (15%) it was abnormal only by one method. Two hundred and fifty-seven patients (46%) presented with decreased RUU in one kidney, associated with a small kidney in 73 patients (13%). RCU was normal in all of these 73 patients (100%, P<0.0001). The sensitivity and specificity of RCU for evaluating renal function in relation to small renal size and with respect to RUU were 72% and 97%, with positive and negative predictive values of 95% and 80%, and an accuracy of 85%. Visual analysis of the 73 studies with decreased RUU and normal RCU showed a small, normal kidney on 55 occasions (75%), cortical scars in eight (11%), and impaired bilateral function in 10 (14%). Visual analysis of 10 studies with normal RUU and decreased RCU showed dilated pyelocalyceal system in seven occasions (70%) and normal kidneys in three (P<0.0001). CONCLUSION: It is concluded that relative 99mTc-DMSA uptake corrected for renal size is a more accurate method for assessing individual renal function. When there is a small kidney, relative 99mTc-DMSA uptake corrected for renal size can distinguish between a normal and a hypofunctioning kidney.