Page 378 - Libro 2

358 PART 5 — ABDOMINAL
Figure 23-16 A renal artery thrombosis (same patient as in Fig. 23-15). A power Doppler image confirms the lack of flow. An arterial thrombosis from a hyperacute rejection was found in surgery.
Venous Thrombosis
Renal vein thrombosis (RVT) is also a rare event, oc- curring in less than 4% of renal transplants. RVT most commonly occurs within the first 24 to 48 hours postop. Patients with RVT may complain of pain or discomfort over the transplant due to the kidney swelling. Causes of RVT include surgical complications, compression by a lymphocele or other pelvic fluid collection, propa- gation of an iliac vein thrombus, hypotension, hyper- coagulable states, or torquing of the vascular pedicle. Sonographic findings include enlargement of the kid- ney, decreased renal cortical echogenicity, an enlarged main renal vein that may or may not contain low-level echoes, and an absence of flow on color, power, or spectral Doppler interrogation of the main renal vein. A very helpful finding confirming this diagnosis is the presence of reversed flow in the renal arteries, resulting in a biphasic waveform (Fig. 23-17). However, reversed diastolic flow in the main renal artery is not a specific finding of RVT and may be seen in other clinical sce- narios (see Table 23-1). However, in these other clinical situations, flow in the main renal vein will be observed.
Renal Artery Stenosis
Renal artery stenosis (RAS) is the most common vas- cular complication following renal transplantation, occurring in approximately 10% of patients. Patients
Figure 23-17 A renal vein thrombosis. A spectral Doppler waveform from a segmental renal artery in the renal sinus demonstrates reversed diastolic flow in this patient who pre- sented with abrupt anuria 3 hours postsurgery. Thrombosis of the main renal vein was found at surgery.
will present with severe uncontrolled hypertension. Causes of RAS include postsurgical scarring or dissec- tion, intimal hyperplasia, progressive atherosclerosis, or rejection. Vessel diameter mismatch or complex ar- terial reconstructions are predisposing risk factors. RAS occurs more commonly in LRD and pediatric renal
TABLE 23-1
Causes for Reversed Diastolic Arterial Flow in Renal Transplants
Renal vein thrombosis
Severe ATN
Hyperacute rejection
Page kidney (compression by surrounding fluid
collection)
ATN, acute tubular necrosis.