**3. Radionuclides imaging**

Functional imaging methods based on nuclear medicine, such as the dynamic renal study which use glomerular filtration agents and tubular secretion agents, are useful and routinely used tools for evaluation of renal transplants. Glomerular agents (99mTc-DTPA) are considered to be ideal ones, since glomerular filtration is defined as the main reflex of renal function and their mechanism of extraction occur through the process of ultrafiltration driven by Starling forces in the glomeruli. The most important regulatory mechanisms in glomerular filtration are renal blood flow and the peripheral vascular resistance of afferent and efferent glomerular arterioles. The normal distribution of these renal agents is intravascular, and they are elimi‐

**Figure 1.** DTPA renal scintigraphy. Phase of preserved arterial blood flow.

nated by the renal parenchyma and excreted through the urinary pathways. The acquisition protocol involves the capture of sequential images within a short time interval immediately after the venous administration of the glomerular agent, providing information about renal perfusion (Figure 1), and of sequential images over a more prolonged period of time in order to obtain information about glomerular filtration and urine formation (Figure 2A). Semiquan‐ titative analysis is performed based on the curves of the radioisotope renogram. These curves are obtained by drawing areas of interest in the kidneys and then tracing time count curves (Figure 2B).

**4. Post-transplant evaluation**

Imaging methods are frequently used in patients with kidney transplantation, even when clinical parameters and laboratorial tests indicate a good evolution. As US is very sensitive, innocuous, and largely available, most of centers for renal transplantation include, at least, one US exam in the immediate prost-transplant period to detect possible subtle complications that otherwise could remain undetected until more severe symptoms [6, 22]. As mentioned early, US is performed with high frequency transducers, using scanners with Color and Power

Imaging in Kidney Transplantation http://dx.doi.org/10.5772/55074 29

The appearance of transplant kidney is quite similar to the native ones. But, in the immediate post-transplant period a mild dilatation of collecting system is expected due to hipotony (Figure 3).and edema in ureteral anastomosis [22]. A detailed examination is performed and, not rarely, incidental findings as kidney stones, cysts or small angiomiolipomas may be detected in first post-surgical examination. Besides, a careful search for perinephric collections is performed and CD and PD used for evaluation of vascular anastomosis. The renal transplant artery is usually anastomosed to the donor external iliac artery in an end-to-side way. Occa‐ sionally, the artery may be anastomosed in an end-to-end way to the internal iliac artery. The donor renal vein is anastomosed in an end-to-side way to the donor's external iliac vein [23].

**Figure 3.** Normal sonographic appearance of a renal allograft in the immediate post-transplant period. Notice the

Complications related to the graft following a renal transplant can be didactically divided into medical complications (MC), urological complications (UC) including fluid collections (FC), and vascular complications (VC). Neoplasms (NEO), and recurrent native renal disease are

**4.1. Normal**

Doppler techniques.

mild dilatation of calyceal system (arrows).

**5. Complications**

**Figure 2.** (A) and (B): 99mTc-DTPA renal scintigraphy. Normal functional phase and renographic curve.
