Effect of extracorporeal piezoelectric lithotripsy shock waves on renal function measured by Tc-99m-DMSA using SPECT

Effect of percutaneous nephrolithotripsy on renal function: assessment with quantitative SPECT of (99m)Tc-DMSA renal scintigraphy

PURPOSE

To measure the effect of PCNL on global and regional renal function using quantitative single-photon emission CT (SPECT) measurement of Tc-dimercaptosuccinic acid (DMSA) uptake by the kidneys (QDMSA).

PATIENTS AND METHODS

A series of 47 male and 41 female patients with a mean age of 47 +/- 16 years were studied by sequential QDMSA examinations before and 1.5 to 24 months after PCNL. Among the 67 patients (76%) in whom PCNL was performed using upper- or lower-pole access, the function of the affected and nonaffected poles of the treated kidney was calculated separately.

RESULTS

There was no statistically significant difference in the uptake by the treated kidneys before versus after PCNL (11.9% +/- 5% v 11.6% +/- 5%; t = 0.9; P = 0.368). The total functional volume of the treated kidney was slightly decreased, from 235 cc +/- 62 cc to 224 cc +/- 59 cc (t = 2.7; P = 0.011). The percent of the injected isotope dose per cubic centimeter of tissue of the treated kidney was not affected (0.051 +/- 0.02 v 0.053 +/- 0.02; t = 0.86; P = 0.296). Regional assessment revealed a statistically significant decrease in the functional volume at the PCNL port of entry (91 cc +/- 30 cc v 82 cc +/- 27 cc; t = 2.64; P = 0.013). Regarding the percent of the injected dose per cubic centimeter of renal tissue, no statistically significant difference was found between the area of the kidney that underwent PCNL and the untreated area of the same kidney (0.049 +/- 0.02 v 0.05 +/- 0.02; t = 0.693; P = 0.494). The function of the contralateral kidneys remained unchanged (13.4% +/- 5.2% v 13.6% +/- 4.8%; t = 0.68; P = 0.5).

CONCLUSIONS

Despite the statistically significant decrease in the functional volume of the surgically treated region, neither total percent uptake nor percent of injected dose were reduced significantly. Further studies with long-term follow-up of treated kidneys are required.

The true clinical significance of renography in nephro-urology

Isotopic renography is a non-invasive technique used routinely by the clinician to provide information about kidney structure and function. Whilst there is no doubt of its value in the accurate measurement of glomerular filtration rate and in the detection of parenchymal abnormalities, its role in the diagnosis of renovascular disease (especially in patients with renal insufficiency), the exclusion of obstruction and the evaluation of the patient with either acute renal failure or renal transplant dysfunction remains unproven. In part, this reflects a failure to standardise protocols and rigorously evaluate diagnostic techniques. Recent developments in ultrasound, computerised X-ray tomography and nuclear magnetic resonance now present the clinician with rival techniques and emphasise the need for the clinical development of isotopic renography.

99mTc-2GAM: a tracer for renal imaging

We propose a renal imaging agent, the 99mTc complex of the bidentate-N,S chelate N-(mercaptoacetyl)glycine (99mTc-2GAM), with the imaging characteristics of 99mTc-DMSA but a faster kidney uptake; chemical evidence supports the formulation of 99mTc-2GAM as [Tc(v)(O)(GAM)2]-. After biodistribution and toxicity studies in animals, 99mTc-2GAM was evaluated in five normal volunteers. 99mTc-2GAM is rapidly cleared from the blood (t1/2 = 9 min) and 50% of the ID is excreted in the urine in the first 2 h. Dynamic data show a rapid renal uptake that increases up to 1 h with no significant wash-out between 1 and 8 h. The uptake in each kidney ranges from 11.3% to 20.7% ID. Low, stable liver uptake is observed. No significant activity is detected in other organs. We showed no differences between 99mTc-2GAM and 99mTc-DMSA compared in three patients with unilateral kidney disease. We conclude that 99mTc-2GAM has good practical and dosimetric features for renal imaging.

Increased renal function in kidneys with ureteropelvic junction obstruction: fact or artifact? Assessment by quantitative single photon emission computerized tomography of dimercapto-succinic acid uptake by the kidneys

PURPOSE

We evaluated whether increased differential renal function on the pentetic acid (DTPA) renogram represents elevated renal function in obstructed kidneys.

MATERIALS AND METHODS

In 10 patients with unilateral ureteropelvic junction obstruction and a differential function of 53% or greater on the DTPA renogram of the obstructed kidney we performed quantitative single photon emission computerized tomography of dimercapto-succinic acid uptake by the kidneys.

RESULTS

The absolute uptake of dimercapto-succinic acid was significantly higher in the obstructed kidneys compared to the contralateral normal kidneys (30.0% +/- 7.8 versus 25.3% +/- 8.2, t = 3.6, p < 0.01, respectively). The elevated absolute uptake in the obstructed kidneys was due to an increased functional volume compared to the contralateral normal kidneys (126.0 +/- 69.7 cc versus 102.3 +/- 59.2 cc, t = 4.4, p < 0.01, respectively).

CONCLUSIONS

The results suggest that increased relative renal function in hydronephrotic kidneys due to ureteropelvic junction obstruction is not an artifact of the DTPA renogram. It may represent a compensatory mechanism that sometimes may overcompensate resulting in a paradoxical hyperfunctioning kidney.

Extracorporeal piezoelectric shock wave lithotripsy as mono and multiple therapy of large renal calculi including staghorn stones in unanaesthetized patients under semi-ambulant conditions

OBJECTIVE

To examine the effectiveness and complication rate of extracorporeal piezoelectric shock wave lithotripsy (EPL) as monotherapy for the treatment of large renal calculi.

PATIENTS AND METHODS

Treatment consisted of semiambulant EPL as monotherapy combined with protective ureteric stenting in 84 patients. Three groups were established according to stone volume (borderline-stone, partial and complete staghorn). An average of 18,230 shock waves was applied in 3.76 sessions to each patient.

RESULTS

No major complications were observed but there were minor complications in 33% of patients. Invasive auxiliary methods were necessary in only 12%. After a mean follow-up of 9 months (n = 72), 54% of patients were stone-free and in 22% the fragments passed spontaneously. Thus the success rate was 76%. Analysis of the three groups showed no difference in stone status during follow-up. There was no relation between the outcome of treatment and stone volume. Analysis of the patients who failed to respond to treatment showed that they were treated for longer than the stone-free group, with significantly fewer sessions per week (0.71 vs 1.28 sessions/week). It appears that higher rates of stone removal can be achieved with more frequent treatment sessions at shorter intervals.

CONCLUSION

We consider semi-ambulant EPL monotherapy to be a minimally invasive alternative treatment in patients with large renal calculi, including staghorn stones.