Foetor uraemicus

A uremic fetus is a typical urine smell of the exhaled air. The foetus is one of the symptoms of uremic gastroenteropathy (Kuhlmann 2015).

The uremic fetus is most common in chronic renal insufficiency. In acute renal failure there is usually no foetus in the first 5 - 7 days - despite high urea levels (Schwiegk 1968).

A foetor uraemicus occurs in the final stage of renal failure (uremia). It is caused by the breakdown of urea to ammonium in saliva (Kasper 2015). Di- and trimethylamines in particular are responsible for the characteristic odor (Deif 2016).

However, there are no parallels between urea concentration and foetor uraemicus (Schwiegk 1968).

In our latitudes, the clinical picture of a uremic fetus is rarely seen nowadays (Herold 2020).

Often the uremic fetus is accompanied by a metallic taste sensation, which is caused by the breakdown of urea and is called

• dysgeusia (Kasper 2015)

Other symptoms of advanced uremia, besides uremic gastroenteropathy, can be:

• visual disturbances
• uremic encephalopathy

Inspection: The typical urine smell of exhaled air is conspicuous (Kuhlmann 2015).

Sonography: Sonographically the kidneys may be reduced in size with a narrowed parenchymal border. The vessels may show arteriosclerotic changes.

For a detailed diagnosis see chronic renal insufficiency.

• CBC (often there is a normochromic, normocytic anemia).
• Vit. D
• FGF 23 (fibroblast growth factor 23, regulates phosphate metabolism (Erben 2019)(Kassumeh 2016)
• Blood glucose determination and if necessary HbA1c- value
• Serum creatinine
• eGFR
• Iron
• Ferritin
• Transferrin saturation
• Vit. B 12
• Folic acid
• Blood gas analysis (risk of metabolic acidosis)
• Potassium (risk of hyperkalemia)
• Chloride (risk of hyperchloremia)(Kasper 2015)
• Calcium
• Serum phosphate analysis (often there is hyperphosphatemia)
• Parathormone (possibly elevated)
• Vitamin D (Weckmann 2019)
• Urinalysis:
  • Proteinuria (Weckmann 2019)
  • Albuminuria (albuminuria is the most important risk factor for progression of CKD and for the development of cardiac risk [Herold 2020])
  • Hematuria (Weckmann 2019).
  • Protein determination in 24 h urine (Woolliscroft 2013).

Should a foetor uraemicus occur in the context of uremic gastroenteropathy, this is an urgent indication for dialysis or for optimizing the dialysis dose (Kasper 2015).

For further therapeutic measures see renal replacement therapy

Patients with chronic kidney disease (CKD) should avoid ulcerogenic drugs such as:

• NSAID
• Steroids
• ASS (basement 2010)

1. Deif O A (2016) Recording and evaluation of uremic retention solutes through an interactive database. Inaugural dissertation of the Medical Faculty Charité in Berlin 49
2. Heirs R G (2019) Physiology and pathophysiology of FGF23 and Klotho. The nephrologist 14: 302 - 304
3. Herold G et al (2020) Internal medicine. Herold Publisher S 431
4. Kasper D L et al (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education S 2426
5. Kasper D L et al (2015) Harrison's Internal Medicine. Georg Thieme Publisher S 2234
6. Kassumeh S et al (2016) Nephrology and Rheumatology. Urban and Fischer Publishing House 46 - 51
7. Kuhlmann U et al (2015) Nephrology: Pathophysiology - Clinic - Kidney replacement procedure. Thieme Publishing House 445
8. Keller C K et al (2010) Practice of nephrology. Springer Publishing House S 212 - 213
9. Schwiegk H et al (1968) Handbook of Internal Medicine: Eighth volume on kidney diseases. Springer Publishing House S 719
10. Weckmann S et al. (2019) S 3- Guideline Care of patients with chronic non-dialysis-related kidney disease in general practice. AWMF register number: 053 - 048
11. Woolliscroft J (2013) Diagnostic and therapeutic lexicon for the family doctor: The most important diseases from A - Z. Springer publishing house S 294 - 295