Refined microscopic urinalysis for red blood cell morphology in the evaluation of asymptomatic microscopic hematuria in a pediatric population

PURPOSE

The use of refined microscopic urinalysis for the presence of dysmorphic red blood cells (RBCs) has been evaluated in children and adults with a known source of hematuria. We examined the clinical usefulness of this study in a pediatric population with an unknown source of hematuria.

MATERIALS AND METHODS

Children 12 years old or younger referred for evaluation of asymptomatic microscopic hematuria exhibiting 4 or more RBCs per high power field were enrolled in this study. Patients provided a first morning urine sample subjected to refined urinalysis for RBC morphology. Standard evaluation of patients was performed until a final diagnosis of the hematuria source was identified.

RESULTS

A total of 44 patients completed the study. Refined urinalysis revealed pure dysmorphic RBCs in 22 patients, pure isomorphic RBCs in 8 and mixed isomorphic/dysmorphic RBCs in 14. The presence of dysmorphic RBCs correctly predicted a glomerulotubular source of hematuria in 29 of 36 patients (sensitivity 83%, specificity 81%), while the presence of isomorphic RBCs predicted a uroepithelial source of hematuria in 2 of 8 patients (sensitivity 25%, specificity 22%). Hematuria and 2+ proteinuria (100 mg./dl.) were more sensitive (100%) and specific (83%) than the presence of dysmorphic RBCs in predicting glomerulotubular hematuria.

CONCLUSIONS

We believe that this is a costly test offering little additional information to the evaluation of microscopic hematuria in children. A thoughtful history and physical examination with microscopic urinalysis and dipstick for proteinuria provide an equal amount of diagnostic information. We do not recommend its routine use in the evaluation of microscopic hematuria in children.

A randomized, prospective, comparative study of manual and automated renal biopsies

A percutaneous renal biopsy can be performed in several ways, including using a spring-loaded biopsy gun. As this form of renal biopsy has become more popular, a controversy has developed regarding tissue adequacy and the incidence of complications. To compare these two aspects in an automated biopsy and a manual biopsy, we studied 166 patients assigned to one of the two renal biopsy methods. In a randomized, prospective manner from June 1994 until February 1997, group 1 (67 patients) received a 14 G Tru-cut needle (Baxter, Deerfield, IL) manual biopsy while group 2 (99 patients) received an 18 G automated gun biopsy. There was no difference in sex, age, hemoglobin level, prothrombin time, partial thromboplastin time, or diastolic and systolic blood pressure prebiopsy in groups I and II. Indications for biopsy were proteinuria (38%), proteinuria accompanied by hematuria (31.3%), acute renal failure (9.6%), lupus nephropathy (9.6%), chronic renal failure (6%), and hematuria only (5.4%). In group I, the number of cores was 1.88 +/- 0.56, the glomeruli obtained were 27.3 +/- 13.8, and the number of glomeruli per core were 15.3 +/- 8.4. In group II, the values were 2.37 +/- 0.88, 20.7 +/- 11.1, and 9.95 +/- 6.9, respectively. These results showed a statistically significant difference (P < 0.05). In all cases, pathological diagnosis was possible. The histology showed IgA nephropathy in 25.9%, minimal change disease in 16.3%, lupus nephritis in 11.4%, membranous glomerulonephropathy in 9.3%, membranoproliferative glomerulonephritis in 5.4%, and others. The incidence of postbiopsy hematoma was marginally greater in group I (22.3% v 11.1%) and the area of perirenal hematoma shown on ultrasound 24 hours postbiopsy was larger in group I, as well (848 +/- 623 mm2 v 338 +/- 260 mm2). Hematocrit levels before and after biopsy showed a significant difference (34.9% +/- 7.9% and 34.0% +/- 7.6%, respectively; P < 0.05) in group I, but no significant difference was observed in group II (35.1% +/- 7.0% and 34.7% +/- 6.9%). Both techniques rendered adequate tissue sampling, but the extent of bleeding was more severe with the manual 14 G Tru-cut needle biopsy.

Efficacy of prone positioning during intravenous urography in patients with hematuria or urothelial tumor but no obstruction

RATIONALE AND OBJECTIVES

The authors prospectively explored the efficacy of using prone positioning during intravenous urography to improve diagnostic visualization and eliminate the need for retrograde pyeloureterography in patients with no obstruction but with hematuria, history of urothelial tumor, or abnormal results of urine cytology.

MATERIALS AND METHODS

Prone radiography was added to the usual intravenous urography protocol in 510 patients (347 men, 163 women) without urinary tract obstruction. Interpretations of intravenous urograms and recommendations for retrograde pyeloureterography were made before and after evaluation of the prone image.

RESULTS

Confidence in the urographic interpretation was improved with acquisition of the prone radiograph in 100 of 510 patients (19.6%) (95% confidence interval, 82.1, 118). Retrograde pyeloureterography was obviated in 46 of 510 patients (9.0%) (95% confidence interval, 33.1, 58.9). The prone image was most helpful in evaluating the distal ureters (sacral and pelvic segments).

CONCLUSION

Prone patient positioning during intravenous urography is useful when complete visualization of the upper urinary tract is desirable. Obtaining the additional image is cost-effective, even when only a few retrograde pyeloureterography studies are obviated.

Clinical audit of the use of renal biopsy in the management of isolated microscopic hematuria

Whether renal biopsies are indicated for the investigation of microscopic hematuria is a subject of debate. In this retrospective study we evaluated our use of renal biopsy in patients who presented between 1985 and 1995 with microscopic hematuria but without proteinuria, hypertension or renal insufficiency. Of 111 patients, 75 had a renal biopsy. Histological diagnoses included thin membrane nephropathy (TMN) (36%), IgA nephropathy (IgAN) (23%), non-IgA mesangioproliferative glomerulonephritis (MPGN) (9%), mild glomerular abnormalities (11%), focal global glomerulosclerosis (FGS) (4%) and normal (17%). After 85 patients had been followed for a mean of 43 months there were no deaths, 3 patients had proteinuria (IgAN 2, no biopsy 1), 1 had proteinuria and renal insufficiency (immune negative MPGN) and 11 were hypertensive (TMN 3, IgAN 2, normal 2, FGS 1, no biopsy 3). Hematuria resolved in 23 patients. Only 11 patients were still attending the nephrology clinic and 27% of the patients who were advised to continue annual follow-up with family doctors had not done so. In summary, the information obtained from renal biopsy rarely altered clinical management. Hypertension developed in 13% of the patients followed but it was not predicted by the biopsy result. Although a renal biopsy will usually be diagnostic it is difficult to justify in patients who have isolated microscopic hematuria.

Is kidney graft biopsy indicated in recipients with newly developed, microscopic hematuria?

We actively performed renal allograft biopsies on 87 living donor renal transplant recipients presenting with stable serum creatinine but showing newly developed recurrent microscopic hematuria with a small amount of proteinuria during the maintenance phase of immunosuppression and found definite pathological lesions in 56 cases (64%). Chronic rejection of a mild grade (n = 27) and various kinds of glomerulonephritis (n = 27) were the major pathological diagnoses, and from 14 cases singular or complicated cyclosporine (CsA) toxicity was found. Twenty-four out of the 27 glomerulonephritis cases were IgA nephropathy, which is the most common glomerulonephritis in Korea. Through this study, the authors found chronic rejection or glomerulonephritis even in grafts which are generally considered to be normal. CsA nephrotoxicity, which was not expected clinically, could be found. In summary, renal allograft biopsy on patients, even with stable graft function when they start to show microscopic hematuria with or without a small amount of proteinuria, should be performed to document the early intragraft events if there are no medical contraindications.

Giant cell arteritis presenting as renal vasculitis

Giant cell arteritis commonly presents with headache, polymyalgia, and visual signs and symptoms. Other neurological, respiratory or vascular symptoms occur in 10-30% of patients. It is extremely rare for giant cell arteritis to present initially with haematuria. Here we describe a case which presented with fever and haematuria, which emphasise the need to be vigilant about the diagnosis of giant cell arteritis as an underlying cause.

Detecting human bladder carcinoma cells in voided urine samples by assaying for the presence of telomerase activity

BACKGROUND

In an attempt to find a more sensitive and specific noninvasive assay for the detection of bladder carcinoma, the authors assayed exfoliated cells from patients' voided urine for the presence of telomerase, an enzyme that maintains a cell's chromosomal length and is thought to be active in the transformation of normal somatic cells into immortal human tumor cells.

METHODS

The authors used a polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP) assay to determine the presence of telomerase activity in voided urine samples from patients with known but yet untreated bladder carcinoma (n = 104) and from patients with hematuria of benign causes (n = 47). For 88 of the patients with bladder carcinoma, cytology was determined independently of the telomerase results or the pathology findings.

RESULTS

Of the 104 bladder carcinoma specimens, 88 (85%) tested positive for the presence of telomerase. Seventy-nine percent (23 of 29) of the Grade 1 tumors, 84% (32 of 38) of the Grade 2 tumors, and 87.5% (28 of 32) of the Grade 3 tumors were positive for telomerase activity. Five patients with carcinoma in situ (100%) were also positive. Telomerase activity was not found in 31 of 47 patients with bladder calculi, benign urethral stricture, benign prostatic hyperplasia, or inflammation. In the 16 patients (34%) who did have a false-positive result when tested for telomerase, all had either chronic or severe inflammation, including 1 patient with an inverted papilloma, 1 patient with cystitis cystica, and 1 patient with cystitis glandularis. However, for 35 normal, healthy volunteers whose voided urine samples were also assayed for the presence of telomerase activity, none was found. By comparison, only 51% (45 of 88) of the cytology samples from patients with bladder carcinoma yielded positive findings, whereas 49% (43 of 88) resulted in false-negative readings for tumors. Only 13% (3 of 23) of the Grade 1 tumors, 44% (14 of 32) of the Grade 2 tumors, and 82% (23 of 28) of the Grade 3 tumors were diagnosed by cytology. All five patients with carcinoma in situ were positive for cytology as well as for telomerase activity. When cytology was compared with the PCR-based telomerase assay in determining the presence of bladder carcinoma, the difference in the overall detection rates (85% for telomerase vs. 51% for cytology) was significant (P < 0.001). Furthermore, when telomerase activity was compared with cytology for low grade lesions (Grades 1 and 2), the difference in the detection rates (82% for telomerase vs. 31% for cytology) was also significant (P < 0.001).

CONCLUSIONS

Urinary cytology yields poor results for low grade tumors. This study shows the possible application of the telomerase assay in detecting bladder carcinoma, in particular low grade tumors, in voided urine samples.

Antithyroid and antiadrenal autoantibodies in antiglomerular basement membrane disease, thin basement membrane disease and Alport syndrome

The basement membranes of the glomerulus, thyroid and adrenal all contain the Goodpasture antigen, the target of autoantibodies in antiglomerular basement membrane (GBM) disease. Antithyroid antibodies can be associated with antiGBM disease, and there have been occasional reports of antithyroid antibodies in Alport syndrome, an inherited kidney disease where the GBM lacks the Goodpasture antigen. The aim of this study was to determine how often antithyroid and antiadrenal autoantibodies occurred in antiGBM disease, Alport syndrome and a related condition, thin basement membrane disease (TBMD). Sera from patients with antiGBM disease (n = 19), Alport syndrome (n = 5) or TBMD (n = 13) were tested for antithyroglobulin, antithyroid microsomal and antiadrenal antibodies. Five of the patients with antiGBM disease (5/19, 26%, P NS) had antimicrosomal, and one had antithyroglobulin, antibodies (1/19, 5%, P NS). No patient with Alport syndrome had antithyroid antibodies. One with TBMD (1/13, 8%, P NS) had antithyroglobulin and antimicrosomal antibodies at titres of 1/400 and 1/25,600, respectively. Both patients with antithyroglobulin antibodies had previously been diagnosed with hypothyroidism. No one with antiGBM disease, Alport syndrome or TBMD had antiadrenal antibodies. Antithyroid microsomal antibodies do not occur significantly more often in patients with antiGBM disease than in normals, and antithyroid and antiadrenal antibodies are not associated with Alport syndrome or TBMD.

Expression of cytokeratin 20 in urinary cytology of patients with bladder carcinoma

BACKGROUND

Of the 20 known cytokeratins, CK-19 is expressed in normal urothelium, whereas the recently identified CK-20 is expressed in urothelial carcinoma cells but not in normal urothelial cells. The aim of this study was to examine whether CK-20 expression could serve as a noninvasive test in which malignant urothelial cells in urine are detected and monitored.

METHODS

In the current study, the authors used reverse transcriptase-polymerase chain reaction (RT-PCR) methods to determine the expression of CK-20 in cells separated from the urine of patients with bladder carcinoma. Cells were obtained from the urine of 87 patients divided into the following 2 groups: 1) 14 healthy volunteers without any known history of transitional cell carcinoma (TCC), and 2) 73 patients with hematuria suspected for TCC of the bladder. For control purposes, CK-20 expression was examined in cells of 1) bladder carcinoma tumors of 5 patients, 2) blood of either patients with bladder carcinoma (n = 5) or healthy controls (n = 5), and 3) three different cell lines. RNA of the various cell pellets was extracted and RT-PCR was performed with CK-20 and CK-19 primers (CK-19 was used as a marker for normal epithelial cells).

RESULTS

CK-20 amplification band (370 bp) was obtained with mRNA extracted from TCC cells of either bladder tumor or HT-29 line (a CK-20 colon carcinoma line). Sensitivity of the method was found to be 91%, whereas specificity was 67%. Among the 7 false-positive cases, 3 showed atypia, 3 hyperplasia, and 1 metaplasia, and 2 underwent previously successful TCC tumor removals, suggesting that the CK-20 test also responded to premalignant lesions. No false-positive cases were found in the healthy control group. No other preparation, including blood of the patients of with TCC, showed the CK-20 amplification band.

CONCLUSIONS

These results indicate that CK-20 is a potential biomarker for noninvasive detection of bladder carcinoma by assaying uroepithelial cells from the voided urine specimen with RT-PCR.

A cluster of haematuria cases in a pesticide-manufacturing plant

In a pesticide manufacturing and formulating facility, 10 employees out of 48 were shown to have haematuria on dipstick testing. They included seven of the 27 production workers, all of whom had worked in both of two particular areas prior to the commencement of the routine urine testing. Five of the seven production workers with haematuria underwent further investigations, and in all five the haematuria was glomerular in origin. Two underwent renal biopsy, which showed irregular attenuation of the glomerular basement membrane (GBM) but no abnormality by light microscopy. Immunofluorescence studies were negative. This case series of glomerular haematuria is not readily explained by chance, false positive dipstick testing, or a recognizable non-occupational cause. Thin GBM disease, which is a benign condition, appears the likely explanation. Thin GBM disease is usually an autosomal dominant condition, but clustering of these genotypes in this small population is improbable.

[Morphologic parameters of blood platelets and dysmorphic erythrocyturia in chronic glomerulonephritis]

Dysmorphic erythrocyturia is known as an attribute of glomerular bleeding. During chronic glomerulonephritis the morphological changes of blood platelets were also observed. The subject of our study was to indicate if the common mechanism leading to blood platelets polymorphology and dysmorphic erythrocytes origination in chronic glomerulonephritis is possible. We estimate the count of blood platelets (PLT), mean platelets volume (MPV), platelet distribution weight (PDW) and platelets crit (PCT) in peripheral blood of 46 patients with chronic glomerulonephritis with dysmorphic erythrocyturia (26 with renal sufficiency and 20 with renal insufficiency) and 32 healthy volunteers. The dysmorphic erythrocyturic erythrocytes were examined in first morning urine. We have not demonstrated the correlation of changes in blood platelets morphology with percent dysmorphic erythrocytes in urine. The results of our investigations do not confirm exactly the common mechanism of the morphological changes which were observed. Minimal changes of the blood platelets parameters may be the results of changes in structure of phospholipids platelets membrane as well as less activation of platelets membrane receptors-GP Ia/IIb and GP Ic/IIa.

Vidarabine therapy for virus-associated cystitis after allogeneic bone marrow transplantation

We describe a method of diagnosing virus-associated cystitis after allogeneic bone marrow transplantation (BMT) and treatment with vidarabine therapy. At 7-10 days post-BMT when cystitis was suspected, we observed urinary sediments by the Papanicolaou stain to detect virus inclusion bodies. When positive, we examined urinary sediments by transmission electron microscope and measured the diameter of viral particles to determine the families. This process needed only 4 days. Among 16 consecutive cases, adenovirus and polyomavirus were each detected in three. Adenovirus caused hemorrhagic cystitis in two cases and cystitis without macroscopic hematuria in one case. Polyomavirus caused cystitis without macroscopic hematuria in one case. Polyomavirus was also detected in two cases without any symptoms. Vidarabine (10 mg/kg/day i.v.) was administered for 5 days as one course. Soon after one course of vidarabine, most symptoms subsided and virus inclusion bodies disappeared in all cases except for one with severe hemorrhagic cystitis. From these experiences, vidarabine reduces excretion of adenovirus and polyomavirus in the urine of BMT recipients and improves clinical symptoms in some cases of cystitis associated with these viruses.

Isolated microscopic haematuria in the genitourinary clinic: the value of renal biopsy

Isolated microscopic haematuria is a common finding in the genitourinary clinic. The conventional approach to investigation includes urological referral for cystourethroscopy if renal imaging is normal. However the diagnostic yield is very low; in particular urothelial malignancy at age < 40 years is rare. Glomerular disease is increasingly recognized as a common cause of microscopic haematuria. In this study 50 patients with persistent microscopic haematuria detected at a genitourinary clinic underwent renal biopsy. Twelve (24%) had an abnormal biopsy--IgA nephropathy 6 (12%), thin membrane nephropathy 3 (6%), other glomerulonephritis 3 (6%). In 7 others no abnormality was found but information was incomplete as electron microscopy was unavailable. It is important to establish these diagnoses since some patients will develop progressive renal disease. In this clinical setting renal biopsy will give diagnostic and prognostic information, protects from repeated urological investigation, and allows reassurance if renal histology is normal. Renal biopsy is recommended for patients age < 40 years with persistent microscopic haematuria. An algorithm for the investigation of microscopic haematuria is presented.

Thin glomerular basement membrane disease: light microscopic and electron microscopic studies

Benign recurrent hematuria usually indicates a good prognosis. This condition is associated with abnormally thin glomerular basement membranes. Of 680 renal biopsy cases in which lower urinary tract disease had been excluded by careful study, 25 cases from seven children and eighteen adults met the criteria for thin glomerular basement membrane disease, placing the incidence of the disease at 3.7%. The mean patient age was 32.4 years and the male to female ratio was 1 to 5.3. The primary finding was microscopic hematuria in eighteen patients and gross hematuria in five patients. Among eighteen patients who had microscopic hematuria, one patient also exhibited proteinuria and one patient suffered from acute renal failure due to acute drug-induced interstitial nephritis. Proteinuria was only found in one patient. All of the patients had normal renal function, with the exception of one who suffered from acute renal failure. The duration of hematuria from the time of detection to the date of biopsy ranged from 3 months to 30 years with a mean interval of 56.6 months. No apparent evidence of familial hematuria in any patient was noted. Under light microscopy most glomeruli were normal. However, five cases showed focal global sclerosis. Under immunofluorescence microscopy seventeen cases were negative for all immunoglobulins, for complement, and for fibrinogen. Eight cases showed nonspecific mesangial deposition of fibrinogen and/or IgM. Ultrastructurally, extensive diffuse thinning of the GBM was a constant finding. The mean thickness of the GBM was 203.2 +/- 28.3 nm (n = 25); the thickness in adult (201.4 +/- 27.5 nm; n = 18) did not differ from that in children (208.1 +/- 32.0 nm; n = 7).

Diagnosis of glomerular haematuria: role of dysmorphic red cell, G1 cell and bright-field microscopy

Differentiation between glomerular and non-glomerular haematuria by observation of the changes in red cell morphology using phase-contrast microscopy is a well established technique. However, the method is not widely accepted in clinical practice because of controversy regarding the minimum percentage of dysmorphic red cells required to diagnose glomerular aetiology, as well as the need for specialized microscopes. Recently, a glomerular-specific morphological alteration of red cells has been described, which has the form of a doughnut shape with one or more blebs and which is termed the "G1" cell. In the present double-blind prospective study 250 urine samples were examined without any knowledge of diagnosis. Haematuria was detected in 122 cases. The type of haematuria was characterized by counting dysmorphic cells and G1 cells separately, in each case using a phase-contrast microscope as well as an ordinary bright-field microscope with and without staining of urinary sediments. The results were later correlated with the confirmed diagnosis. The study showed that the G1 cell is more specific than the dysmorphic cell for the diagnosis of glomerular haematuria. Evaluation of both dysmorphic red cells and G1 cells can be done using bright-field microscopy with 100% specificity and sensitivities of 82 and 100%, respectively. It has been concluded that the ordinary bright-field microscope can be used for the diagnosis of glomerular haematuria with an efficiency similar to that of a phase-contrast microscope.

A 51-year-old woman with nephrotic syndrome, hematuria, and renal insufficiency

This case illustrates the utility of all modalities of the renal biopsy in arriving at a correct diagnosis in an adult patient with nephrotic syndrome. Unlike the clinical situation in children, where minimal change disease is presumed to underlie the nephrotic syndrome unless the patient shows steroid resistance, the list of differential diagnosis of nephrotic syndrome in the adult is lengthy. The renal biopsy is essential in establishing the specific diagnosis. We discuss the diagnostic approach in an adult patient with a relatively uncommon disease causing the common manifestations of nephrotic syndrome, hematuria and renal insufficiency.

Effects of SWL on glomerular filtration rate and renal plasma flow in uninephrectomized minipigs

This study tested the hypothesis that the effects of SWL on hemodynamics in solitary kidneys differ from those in kidneys of binephric animals. Five female miniature pigs (Pitman-Moore, 6 months of age, 30-35 kg) were anesthetized for unilateral nephrectomy. Seven pigs served as binephric controls. Two weeks later, each pig was anesthetized, prepared for unilateral or bilateral urine collections, and subjected to SWL (Dornier HM3, 2000 shocks, 24 kV). Clearances of inulin (glomerular filtration rate; GFR) and para-aminohippurate (renal plasma flow; RPF) were measured 1 hour prior to and 1, 4, and 24 hours after SWL. The GFR and RPF were higher in uninephrectomized than in intact pigs at all time points. In both groups, SWL reduced GFR and RPF. In the binephric pigs, RPF was reduced at all times post-SWL, but in the uninephrectomized pigs, RPF was returning toward baseline by 4 hours post-SWL and was not different from baseline at 24 hours. A comparison of whole-animal GFR and RPF (righ plus left clearances in binephric pigs v solitary renal clearances in uninephrectomized pigs) showed that whole-animal GFR and RPF did not differ between the groups before or after SWL. Compensatory renal hypertrophy and improved hemodynamics in solitary kidneys may acutely attenuate the renal vasoconstrictive effect of SWL. The long-term consequences of the compensatory changes are unknown.

Semiautomatic quantitation of macrophages in human renal biopsy specimens in proteinuric states

AIMS

To develop and validate a rapid and economical semiautomated approach to the measurement of immunostainable tissue components which is applicable to routine diagnostic practice. To apply this approach to the measurement of macrophages in renal biopsy specimens in nephrotic states, as protein in the renal tubules may induce macrophage infiltration, and the morphology of macrophages in tissue sections does not lend itself to cell counting.

METHODS

Macrophages were identified by immunostaining with a pan-macrophage marker, followed by digital image capture and analysis using a macro procedure written for the freeware image analysis program NIH-Image.

RESULTS

The method was rapid, robust and accurate to within the limits imposed by sampling error inherent in the use of small needle biopsy specimens. Very few macrophages are found in normal kidney (mean volume fraction (+/- 95% confidence limits) 0.04% (0.02%)) but infiltration of macrophages was detected in minimal change nephropathy (0.29% (0.12%)) and in membranous glomerulonephritis (0.42% (0.11%)). A statistically significant correlation was found between macrophage volume fraction and weight of proteinuria in minimal change nephropathy but not in membranous glomerulonephritis. Correlations were found in both diseases between macrophage volume fraction and serum creatinine at time of biopsy.

CONCLUSIONS

The equipment is inexpensive and measurement takes less than one minute per biopsy specimen. The results indicate that macrophage infiltration is part of the pathological process in minimal change nephropathy and membranous glomerulonephritis. The correlation with creatinine at time of biopsy suggests that renal impairment in minimal change nephropathy may result from infiltration by immunologically active cells and not merely from haemodynamic changes in nephrons. However, the correlation is not close, indicating that the relation between macrophage infiltration and disease severity is not a simple one.

Remnants of Albunex nucleate acoustic cavitation

Mice were injected with 0.1 mL Albunex and exposed to 200 pulses from a piezoelectric lithotripter at times ranging from 5 min to 24 h following injection. Each pulse was approximately 1.5 sinusoidal oscillations at a fundamental frequency of approximately 0.1 MHz with pressure amplitude of approximately 2 MPa. Although the contrast agent ceases to be an effective scatterer of diagnostic ultrasound after a few minutes in the circulation, the modest lithotripter exposures caused significant hemorrhaging in bladder, mesentery and intestine for periods of up to 4 h after injection. The results demonstrate either that highly stable bubbles much smaller than resonance size or air-containing fragments of the shells of Albunex serve as effective nuclei for acoustic cavitation.