A. Renal function imaging (renal dynamic and static imaging)
1.The principle of imaging:
Intravenous injection of glomerular or tubular secretion type imaging agent, ECT rapid and continuous acquisition of radioactive images, including both kidneys, ureter and bladder, can be sequentially observed in the uptake, secretion and excretion of the imaging agent in the kidney the whole process, not only can provide the morphological image of the urinary system, but also can provide information and quantitative indicators about renal blood perfusion, parenchymal function and urinary excretion and other aspects.
2.Normal images.
Perfusion phase: about 2 seconds after the upper abdominal aorta is visualized, both kidneys are visualized, longer than 4 seconds suggests abnormal renal perfusion; normal perfusion curve is visible with obvious perfusion peaks.
Functional phase: The radioactivity in the kidney gradually increases after the renal perfusion is visualized, and after 2-3 minutes, the kidney shadow is the most dense, with complete morphology and uniform distribution of radioactivity in the kidney, after which the radioactivity around the kidney shadow gradually decreases, and the radioactivity in the renal calyx and pelvis gradually increases, followed by the bladder shadow gradually becomes obvious. 8-10 minutes, the radioactive density in the kidney decreases by more than half.
3.Renogram characteristics.
Normal renogram: steeply rising a segment, after a steeper rising uptake b segment radioactivity reaches a peak, forming a sharp peak shape, peak time mostly in 2-3 minutes, followed by a falling c segment, the peak of the curve drops more than half in 8 minutes, the two renograms are basically similar.
Abnormal renogram:
Rapidly rising type: a segment is basically normal, b segment is continuously rising, no falling c segment. See in urinary tract obstruction.
High level prolongation type: a segment is basically normal, b segment rises insignificantly, b and c segments fuse in an approximate horizontal line. Most often seen in patients with urinary tract obstruction with impaired renal function. Parabolic type: a segment is lower than normal, b segment rises slowly, the peak is posteriorly shifted, the peak is rounded, and c segment falls slowly. It is mainly seen in renal ischemia, impaired renal function, and upper urinary tract incompetence.
Low level prolongation type: a segment is significantly lower, and then there is a horizontal prolongation line that is a fusion of b and c segments. This is common in cases of severely impaired renal function.
Low-level descending type: segment a is significantly lower, segment b does not appear and slowly descends. Seen in kidney function has been lost or no kidney.
Step-down type: a and b segments are normal, and c segment shows irregular step-down. Mostly seen in functional urinary tract spasm.
Small renogram: The contrast between the two sides of the renogram is significantly different, the amplitude of one side of the renogram is significantly lower than the other side, and the peak drop is about 30% or more, but the graph is normal. It is seen in unilateral renal artery stenosis.
4. Clinical application:
Renal function measurement.
GRF and ERPF are important renal function parameters, which can be easily measured by nuclear medicine methods. Studies have shown that they are well positively correlated with Ccr, scr and the highest urine specific gravity, and GFR reflects renal function more sensitively than Ccr and other indicators.
Renal vascular obstruction.
This method is simple and has a diagnostic compliance rate of nearly 100%, especially renal artery branch embolization is superior to IVP, and this method can also be used to observe the efficacy of thrombolysis.
Diagnosis of upper urinary tract obstruction.
The diagnostic sensitivity of upper urinary tract obstruction is about 80-90%. When there is no combined renal impairment, the diagnostic sensitivity of obstruction is comparable to that of IVP, but when there is renal impairment, IVP cannot be visualized in some patients, while ECT can be visualized as long as there is 3% residual renal function.
The use of diuretic nephrography can distinguish mechanical from functional obstruction.
Diagnosis of nephrogenic hypertension.
Nephrogenic hypertension has renal vascular hypertension and renal parenchymal disease hypertension. If one side of the kidney has poor perfusion, significantly smaller renal shadow than the opposite side and delayed clearance of radioactivity in the renal parenchyma, the possibility of renal vascular hypertension is high, and dozens of reports have shown that the true positive rate of renal function imaging for this is 54-100% (85%), and the kepodin (Captopril) test, further improves the diagnosis The Captopril test further improves the correct diagnosis.
Transplant kidney monitoring.
The main complications after transplantation are acute tubular necrosis and rejection reaction. Since renal imaging can comprehensively observe various conditions before, after and kidney, and is a non-invasive test, it is listed as a routine monitoring method for kidney transplantation in foreign countries. The first examination is performed within 24 hours after transplantation, and the results are basically normal indicating successful transplantation, if there is no perfusion and function within a few hours indicating unsuccessful transplantation, the transplanted kidney should be immediately The second examination is performed within 5-6 days to detect acute rejection in time, and later depending on the condition, to detect complications and treat them in time.
Observe the efficacy of treatment of kidney diseases.
Since renal imaging can comprehensively observe various conditions of prenephrosis, nephrosis and postnephrosis, and is non-invasive, it can be used for the etiological analysis of glomerulonephritis, pyelonephritis and various causes of nephrosis and the judgment of renal function and the observation of therapeutic efficacy. For example, if diabetes mellitus combined with pre-renal disease, GFR rises by about 25%, the application of angiotensin-converting enzyme inhibitor to treat the increased glomerular filtration rate at this time can prevent the occurrence of nephropathy.
Static imaging of the kidney
Imaging principle: intravenous injection of slow passage of renal imaging agents, so that they are concentrated in the renal parenchyma for a longer period of time, using ECT imaging for renal parenchymal images.
Clinical applications.
To understand the location, size and morphology of the kidney; diagnosis of renal malformation and renal atrophy.
Differential diagnosis of upper abdominal masses and kidney.
Differential diagnosis of occupying lesions, ischemic lesions and destructive lesions in the renal parenchyma.
Further confirmation of reduced renal function on one side.
C. Bladder-ureteral-renal reflux imaging (indirect method)
Imaging principle: after injection of renal imaging agent, wait for the natural discharge into the bladder, the amount reaches a certain level, artificially increase the abdominal pressure and urination, while using ECT to continuously observe the ureter and kidney area radiological changes.
Clinical application: 35% of patients with urinary tract infection have urinary reflux, the positive rate of this method is about 30%, there are false negatives, but the direct method is consistent with the results of the X-ray method.