Sonography: In CPN, the kidneys appear small on sonography, with focally thin, echogenic cortex (Manski 2019).
In XPN, a kidney can be visualized enlarged and shows an echogenic spatial structure indistinguishable from a (renal) tumor . Sometimes a nephrolithiasis may be presentable (Manski 2019). For further clarification, a CT scan is recommended. (Kuhlmann 2015)
i. v. pyelogram: The i. v. pyelogram (also called urogram) is now rarely used. CT or MRI have taken its place (Manski 2019).
CPN: In chronic PN, calyx deformities often exist in the i. v. pyelogram. These can show different degrees of severity. Plump calyxes are found with necks approaching each other. Often there is already a loss of parenchyma (Keller 2010). Especially at the renal poles, the cortex appears thin and the kidneys are small overall (Manski 2019).
XPN: In XPN, nephrolithiasis is found in the urogram in 40 % - 70 %.
Contrast of the affected side is absent in 30 % - 80 % of patients. The renal shadow appears predominantly enlarged (Manski 2019).
Contrast-enhanced CT (CPN): In CPN, changes found on CT include:
- Plumping of the renal calices
- Deformities of the renal calices
- Narrowing of the parenchyma (Herold 2020).
XPN: XPN shows a mass with inhomogeneous accumulation of contrast medium. Sometimes the presence of renal cell carcinoma cannot be excluded.
Lithiasis is detected much more frequently. The renal function itself is usually reduced in the affected kidney (Manski 2019).
Magnetic resonance imaging: MRI is superior to CT in:
- Questioning extrarenal spread.
- Evaluation of changes in the area of the renal pelvic caliceal system (Pallwein- Prettner 2011).
It can also be used as an alternative to CT- examination, especially in cases of contrast agent intolerance ((Pallwein- Prettner 2011)) and pre-existing renal insufficiency (Manski 2019). In this case, MRI offers an additional possibility of differentiation between inflammatory and neoplastic processes with the help of diffusion-weighted MR imaging (Pallwein- Prettner 2011).
Renal scintigraphy (also called isotope nephrogram = ING)
With this examination method, a side-separated function of the kidney tissue can be performed.
ING is the most sensitive method to detect scarring parenchymal destruction (Manski 2019).