Rare, severe, chronic kidney infection characterised by the diffuse destruction of renal parenchyma.
Most cases are unilateral, resulting in a non functioning kidney, usually associated with chronic obstruction secondary to renal calculi.
Histologically characterised by lipid laden foamy macrophages (xanthoma cells) mixed with other neutrophils, lymphocytes and plasma cells.
Infection begins with the collecting system and calyces and extends into the parenchyma destroying it and adjacent tissues (perinephric abscesses common).
Radiologically XGP can mimic all other inflammatory conditions of the kidney as well as malignancy. Histologically, the lipid laden macrophages may resemble clear cells.
Most often seen in middle aged women with a history of recurrent UTIs and stones.
Pathophysiology
Primary factors involved in the development of XGP are infection, obstruction and nephrolithiasis.
- Over 80 % associated with stones, usually staghorns.
- Proteus and E.coli most common cultured organisms (also pseudomonas, klebsiella).
Primary obstruction, followed by infection, leads to recruitment of macrophages with microabscesses and tissue destruction.
- Histologically – fibrosis around the collecting system, multiple small abscesses, papillary necrosis and calyces filled with purulent material, granulomas
May be diffuse or may affect only a focal part of the kidney i.e. parenchyma surrounding one calyx or one moiety of a duplex.
Clinical presentation
Flank pain, fevers and chills are usual symptoms.
Persistent bacteriuria is common.
Additional vague systemic symptoms also common – anorexia, weight loss, malaise.
Flank mass may be noted on exam, and a history of renal stones is usual.
Imaging
CT classic triad:
- Unilaterally enlarged kidney
- Non functioning kidney
- Large renal stone
Other CT features:
- Renal parenchyma replaced by multiple hypodense masses – dilayed calyces and abscesses
- The cavities don’t enhance but the tissue around does – granulomas quite vascular
- “Bear paw” sign – hydronephrotic pattern of hypodense masses
Differential diagnosis – may easily mimic RCC, lymphoma, malakoplakia, TB.
NB the diagnosis of XGP is technically a pathological diagnosis.
Management
Thorough work-up – operative optimisation and ensuring the diagnosis.
- Manage acute presentation and infection
- Manage sepsis with resuscitation, antibiotics
- Drain large perinephric abscesses if needed, nephrostomy etc
- Pre-operative optimisation
- Anaesthetic review
- Optimise nutrition
- Optimal imaging
- Correct anaemia, blood available
The treatment is (“simple”) nephrectomy:
- Prepare for a challenging case
- Visceral injuries are more likely and inflammatory masses may involve adjacent organs requiring resection (spleen, bowel etc)
- Open nephrectomy has been traditional management – laparoscopic nephrectomy now often utilised but higher conversion rates to open cf. RCC
Partial nephrectomy described but generally not recommended.