Infections and the Kidney

Abstract

Infections of the kidney and urinary tract are a common cause of morbidity, and sometimes mortality, especially in young women. The responsible pathogens include bacteria, viruses, protozoa, parasites, and fungi. The clinical nature of the infection can be different in the immunosuppressed, in the setting of kidney transplantation, and in other conditions, including vasculitis, glomerulopathy and cancer. Some infections can lead to systemic immune activation, which can in turn lead to kidney disease.

Questions

• 1. A 55 year old man presented to the emergency room with fever, non-productive cough, anosmia, muscle aches and fatigue for one day and sore throat for 3 days. He had been to his local pub 5 days previously. His temperature was 38.3 °C, BP 124/76, respiratory rate 28/min and oxygen saturation 88%. Chest radiograph was suggestive of bilateral lower lobe interstitial pneumonitis. Laboratory results revealed haemoglobin 13.3 g/dL; white cell count 4.1 × 10⁹/L; lymphocyte count 1.3 × 10⁹/L; blood glucose 12.2 mmol/L; serum creatinine 98 μmol/L; CRP 185 mg/L. Three days after admission he was breathless and transferred to ITU, his creatinine increased to 210 μmol/L.

  What is the most likely cause of his illness?

  • A. COVID-19

  • B. Cytomegalovirus infection

  • C. Staphylococcus infection

  • D. Pneumococcus infection

  • E. Malaria

  Answer: A

  A nasal swab PCR confirmed the diagnosis of COVID-19. He was admitted to the intensive care unit and commenced on intravenous fluids, high flow oxygen via a nasal cannula, enoxaparin 20 mg subcutaneously, dexamethasone 6 mg daily intravenously and insulin adjusted according to glucometer readings. He was transferred out of ICU after 5 days and continued to improve in hospital.

• 2. A 30 year old black woman, recipient of a deceased donor kidney transplant 3 months previously, was noted to have a decline in her baseline kidney function at a clinic visit. She had received antithymocyte globulin, high dose steroid induction therapy and was being maintained on tacrolimus, mycophenolate mofetil (MMF) and prednisolone. She had been noted to be CMV IgG positive while on dialysis. Her BP was130/60 mmHg, pulse 78/min and temperature 39 °C. Laboratory tests: haemoglobin 11.8 g/dL; WCC 3.1 × 10⁹/L; platelet count 130,000; serum creatinine 180 μmol/L from a previous baseline of 110 μmol/L. Urine examination revealed 50 red cells/HPF and proteinuria of 0.5 g/day. Tacrolimus levels were between 5 and 15 ng/mL. She underwent a kidney biopsy.

  Histology of the allograft biopsy showed a peritubular mononuclear interstitial infiltrate; some tubular cells had intranuclear inclusions.

  What is the most likely diagnosis?

  • A. Acute cellular rejection

  • B. Acute antibody mediated rejection

  • C. BK virus infection

  • D. Cytomegalovirus infection

  • E. Tacrolimus toxicity

  Answer: D

  CMV viral load was 15,000 copies/mL. She was treated with intravenous ganciclovir 5 mg/kg every 12 h for 14 days, and thereafter maintained on valganciclovir 900 mg daily for 30 days. MMF was discontinued, tacrolimus dose was optimized according to blood levels, and she continued with low dose prednisolone. Her serum creatinine stabilized at 125 μmol/L.

• 3. An 18-year old boy, recipient of a second (deceased donor) kidney transplant was noted to have an asymptomatic rise in his serum creatinine during a routine clinic visit 12 months after transplantation. He had received antithymocyte globulin, high dose steroid induction therapy and was being maintained on tacrolimus, mycophenolate mofetil (MMF) and prednisolone. He had been noted to be CMV IgG positive previously. He was noted to have haemoglobin 12.8 g/dL; WCC 5.1 × 10⁹/L; platelet count 230,000; serum creatinine 220 μmol/L from a previous baseline of 120 μmol/L. Urine cytology showed epithelial cells with viral inclusions ‘decoy cells’, Allograft biopsy showed mononuclear interstitial inflammation, and some degree of tubulitis with basophilic changes of the tubular epithelium.

  What is the most likely diagnosis?

  • A. Acute cellular rejection

  • B. Acute antibody mediated rejection

  • C. BK virus infection

  • D. Cytomegalovirus infection

  • E. Tacrolimus toxicity

  Answer: C

  He had a urine BK load of 11⁷ copies/mL and a serum BK viral load of 10⁵ copies/mL. His MMF dose was halved, and tacrolimus trough levels lowered and he was treated with leflunomide 100 mg daily for 5 days and 40 mg daily thereafter until the virus was cleared. His kidney function gradually stabilized to around his baseline levels and surveillance for BKV is carried out on a monthly basis.

• 4. A 45 year old black man was recently diagnosed with HIV infection and referred to a Renal Clinic with proteinuria and renal dysfunction. He had minimal ankle oedema, BP 126/82 and had 3 g proteinuria/day. His serum albumin was 25 g/L, serum cholesterol 4.1 mmol/L, serum creatinine 188 μmol/L, eGFR 42.1 mL/min/1.73 m², CD4 count 180 cells/mL, viral load 125,000 copies/mL. He underwent a kidney biopsy.

  What is the most likely biopsy diagnosis?

  • A. Crescentic glomerulonephritis

  • B. Focal segmental glomerulonephritis

  • C. Membranous glomerulonephritis

  • D. Membranoproliferative glomerulonephritis

  • E. Minimal change disease

  Answer: B

  His kidney biopsy showed typical HIV associated nephropathy, with glomerular collapse, microcystic tubular dilatation and interstitial inflammation. He was commenced on Losartan 50 mg daily, and Abacavir 300 mg BD, Lamuvidine (3TC) 150 mg daily and Dolutegravir 50 mg daily. Avoid fixed dose combinations if GFR < 50 mL/min, and tenofovir if possible. His APOL1 genotype was not available.

• 5. A 25 year old man was admitted to the emergency room with a fever of 39.1 °C, and dehydration. He had been on a beach vacation in Mozambique 2 weeks previously. He was noted to have tachycardia of 100/min, BP 96/60 and was pale and had a 2 cm splenomegaly. His haemoglobin was 10.1 g/dL; white cell count 4.1 × 10⁹/L; platelets 92,000; serum bilirubin 35 mmol/L; blood urea 32 mmol/L; serum creatinine 220 μmol/L.

  What is the most likely cause of his acute kidney injury?

  • A. Cytomegalovirus infection

  • B. Epstein barr virus infection

  • C. Malaria

  • D. Pneumococcal infection

  • E. Staphylococcus infection

  Answer: C

  A thin smear revealed the presence of tropozoites of P falciparum. He was commenced on intravenous fluids and therapy with artesunate 2.4 mg/kg intravenously immediately and 12 hourly for 24 h and thereafter switched to oral treatment with artemether-lumefantrine for 3 days. A blood smear at 72 h demonstrated that the parasitaemia had been eradicated and he made a a full recovery.

• 6. A 45 year old man, a visitor from Egypt, was hospitalized with abdominal distension. He had been an agricultural worker. He was noted to have hepatosplenomegly. Investigations showed dipstick proteinuria of 3+, and was measured to be 2.9 g/24 h; serum albumin 35 g/L; serum globulins 50 g/L; haemoglobin was 10.8 g/dL; white cell count 4.1 × 10⁹/L; platelets 112,000; serum bilirubin 10 mmol/L; blood urea 5 mmol/L; serum creatinine 88 μmol/L. Ultrasound of the liver was suggestive of hepatic fibrosis, and was confirmed by fibroscan. A kidney biopsy showed membranoproliferative glomerulonephritis.

  What is the cause of the renal disease?

  • A. Cytomegalovirus infection

  • B. Hepatitis B infection

  • C. HIV infection

  • D. Malaria

  • E. Schistosomiasis

  Answer: E

  A stool specimen showed the presence of schistosoma mansoni. He was treated with praziquantel and advised to avoid future schistosomal infection, and to return to his physician for review.

• 7. A 25 year old forest worker in the Democratic Republic of the Congo presented to the Emergency Department with 3 day history of headache, fever, shivering at night, muscle ache and joint pains. The headache was worst behind the eyes and he also mentioned shivering at night. His temperature was 40.0 °C with a BP of 100/60 and regular tachycardia of 120/min. By Day 4 he had developed a maculo-papular rash with patches of purpura. Haemoglobin 13.0 g/dL, WBC 4.0 × 10⁹/L, platelets 80 × 10⁹/L [normal: 150–400]. Creatinine 350 μmol/L with urea 40 mmol/L, eGFR 24 mL/min/1.73 m². There was proteinuria 0.6 g/L and RBC 50–100/μL. Renal biopsy was not considered as it was felt that it would not influence treatment; furthermore it would add an unnecessary hazard for someone already at risk of bleeding.

  What is the most likely diagnosis?

  • A. COVID 19 infection

  • B. Dengue fever

  • C. Ebola virus infection

  • D. Malaria

  • E. Tuberculosis infection

  Answer: B

  He was diagnosed with Dengue fever and managed with supportive treatment and scrupulous attention to clinical signs, pulse, blood pressure and urine output replacing fluid as necessary but avoiding overload. There is unfortunately no specific treatment for dengue virus and as yet no vaccine.

• 8. An 18 year-old female presented with history of fever for 2 weeks, and the passage of brown urine for 6 days, generalized body swelling for 5 days followed by reduced urine output and breathlessness for 2 days. She had a seizure episode a few hours before presentation. She had noted skin infections 3 weeks preceding the above symptoms. On presentation, she had impaired consciousness (GCS 8/15) but recovered within a few hours. She was pale, with bilateral pitting leg oedema temperature of 37.8 °C, respiratory rate 38 breaths/min, pulse 110 bpm and BP 160/110 mmHg. Urinalysis showed blood, protein, and microscopy revealed red cell casts. Her blood tests showed sodium: 122 mmol/L, potassium: 5.6 mmol/L, HCO₃: 12.4 mmol/L, chloride: 84.4, iCa: 1.01, BUN: 63.3 mmol/L, creatinine: 884 μmol/L, haemoglobin: 8.3 g/dL, leukocytosis with neutrophila of 78%.

  What is the most likeley investigation which will help with diagnosis?

  • A. ASO titre

  • B. ANCA

  • C. Hepatitis B serology

  • D. Kidney biopsy

  • E. Serum immunoglobulin

  Answer: A

  Her ESR was 125 mm/hr and qualitative ASO titre: elevated/positive

• 9. An 18 year-old female presented with history of fever for 2 weeks, red-brown coloured urine for 6 days, generalized body swelling for 5 days followed by reduced urine output and breathlessness for 2 days. She had a seizure episode a few hours before presentation. She had noted skin infections 3 weeks preceding the above symptoms. On presentation, she had impaired consciousness (GCS 8/15) but recovered within a few hours. She was pale, with bilateral pitting leg oedema temperature of 37.8 °C, respiratory rate 38 breaths/min, pulse 110 bpm and BP 160/110 mmHg. Urinalysis showed blood, protein, and microscopy revealed red cell casts. Her blood tests showed sodium: 122 mmol/L, potassium: 5.6 mmol/L, HCO₃: 12.4 mmol/L, chloride: 84.4, iCa: 1.01, BUN: 63.3 mmol/L, creatinine: 884 μmol/L, haemoglobin: 8.3 g/dL, leukocytosis with neutrophila of 78%.

  What is the most likely diagnosis?

  • A. Haemolytic uraemic syndrome

  • B. IgA nephritis

  • C. Lupus nephritis

  • D. Post infectious glomerulonephritis

  • E. Polyarteritis nodosa

  Answer: D

  Her ESR was 125 mm/hr and qualitative ASO titre: elevated/positive

• 10. A 42 year old rural drainage engineer, living in Sao Paulo state in southern Brazil, presented to the Dermatology clinic giving a history of intermittent skin rash sometimes associated with a change in pigmentation. He was found to have heavy proteinuria and referred to the nephrologist. In recent months he had been feeling more tired than usual. He had a pale complexion. There was mild oedema of the ankles. Temperature: 36.5 °C, Haemoglobin 100 g/L, sodium 140 mmol/L, Potassium 5.3 mmol/L, bicarbonate 22 mmol/L, creatinine 216 μmol/L, albumin 23 g/L. Urine protein amounted to 10.5 g/24 h. An MSU revealed neither cells nor blood or glucose; the urine was sterile on culture. A repeat of the investigations a week later gave similar results.

  What is the most likely diagnosis?

  • A. Leptospirosis

  • B. Systemic lupus erythematosus

  • C. Nephropathy of tuberculoid leprosy

  • D. Amyloidosis secondary to lepromatous leprosy

  • E. Falciparum malaria

  Answer: D Amyloidosis secondary to lepromatous leprosy

A. Leptospirosis	Incorrect	Lack of fever, and no active urinary sediment
B. Systemic lupus erythematosus	Incorrect	No joint pain, no fever, no significant urinary sediment
C. Nephropathy of tuberculoid leprosy	Incorrect	Nephrotic syndrome not common in the tuberculoid form of leprosy
D. Amyloidosis secondary to lepromatous leprosy with nephrotic syndrome	Correct	Frequency of amyloidosis in leprosy types: lepromatous [36%], tuberculoid and borderline [5%]. The nephrotic syndrome is a consequence of the amyloidosis.
E. Falciparum malaria	Incorrect	No fever or other evidence of malaria

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