Renal anatomy
The tables below show the anatomical relations of the kidneys:
Right kidney
Direct contact Layer of peritoneum in-between
Right suprarenal gland Liver
Duodenum Distal part of small intestine
Colon
Left kidney
Direct contact Layer of peritoneum in-between
Left suprarenal gland Stomach
Pancreas Spleen
Colon Distal part of small intestine
Renal physiology
Renal blood flow is 20-25% of cardiac output
Renal cortical blood flow > medullary blood flow so, tubular cells more prone to
ischaemia
1
, Proteinuria
Proteinuria is an important marker of chronic kidney disease, especially for diabetic
nephropathy.
NICE recommend using albumin: creatinine ratio in preference to protein: creatinine
ratio (PCR) when identifying patients with proteinuria as it has greater sensitivity.
For quantification and monitoring of proteinuria, PCR can be used as an alternative,
although ACR is recommended in diabetics.
Urine reagent strips are not recommended unless they express the result as an ACR
Approximate equivalent values
ACR (mg/mmol) PCR (mg/mmol) Urinary protein excretion (g/24 h)
30 50 0.5
70 100 1
Collecting an ACR sample:
by collecting a 'spot' sample it avoids the need to collect urine over a 24 hour
period in order to detect or quantify proteinuria
should be a first-pass morning urine specimen
if the initial ACR is > 30 mg/mmol and < 70 mg/mmol, confirm by a subsequent early
morning sample. If the initial ACR is > 70 mg/mmol a repeat sample need not be
tested
Interpreting the ACR results:
in non-diabetics an ACR > 30 mg/mmol is considered clinically significant
proteinuria
in diabetics microalbuminuria (ACR > 2.5 mg/mmol in men and ACR > 3.5 mg/mmol
in women) is considered clinically significant
BP targets
CKD with proteinuria ACR ≥70 mg/mmol or diabetes ---- blood pressure target < 130/80
mmHg.
The NICE guidelines recommend that a blood pressure target < 140/90 mmHg should
be used in non-diabetic patients with CKD and an ACR <70 mg/mmol.
NOT for lower systolic (<120 mmHg) or diastolic (<60 mmHg)
2
, Haematuria
The management of patients with haematuria is often difficult due to the absence of
widely followed guidelines.
It is sometimes unclear whether patients are best managed in primary care, by
urologists or by nephrologists.
The terminology surrounding haematuria is changing.
Microscopic or dipstick positive haematuria is increasingly termed non-visible
haematuria
whilst macroscopic haematuria is termed visible haematuria
Non-visible haematuria is found in around 2.5% of the population.
Causes of transient or spurious non-visible haematuria
UTI
menstruation
sexual intercourse
vigorous exercise (this normally settles after around 3 days)
Spurious causes - red/orange urine, where blood is not present on dipstick
foods: beetroot, rhubarb
drugs: rifampicin, doxorubicin, Metronidazole
Causes of persistent non-visible haematuria
1) cancer (bladder, renal, prostate)
2) stones
3) benign prostatic hyperplasia
4) prostatitis
5) urethritis e.g. Chlamydia
6) renal causes: IgA nephropathy, thin basement membrane disease
Management:
Current evidence does not support screening for haematuria.
The incidence of non-visible haematuria is similar in patients taking aspirin/warfarin to
the general population hence these patients should also be investigated.
Testing
1) urine dipstick is the test of choice for detecting haematuria
persistent non-visible haematuria is often defined as blood being present in 2 out of
3 samples tested 2-3 weeks apart
2) BP , RFTs, and albumin:creatinine (ACR) or protein:creatinine ratio (PCR) should also
be checked
3) urine microscopy may be used but time to analysis significantly affects the number of
RBCs detected
3
, NICE urgent cancer referral guidelines
1) of any age with painless macroscopic haematuria
2) patients under the age of 40 years with normal renal function, no proteinuria and who
are normotensive do not need to be referred and may be managed in primary care
3) aged 40 years and older who present with recurrent or persistent UTI associated with
haematuria
4) aged 50 years and older who are found to have unexplained microscopic haematuria
4
The tables below show the anatomical relations of the kidneys:
Right kidney
Direct contact Layer of peritoneum in-between
Right suprarenal gland Liver
Duodenum Distal part of small intestine
Colon
Left kidney
Direct contact Layer of peritoneum in-between
Left suprarenal gland Stomach
Pancreas Spleen
Colon Distal part of small intestine
Renal physiology
Renal blood flow is 20-25% of cardiac output
Renal cortical blood flow > medullary blood flow so, tubular cells more prone to
ischaemia
1
, Proteinuria
Proteinuria is an important marker of chronic kidney disease, especially for diabetic
nephropathy.
NICE recommend using albumin: creatinine ratio in preference to protein: creatinine
ratio (PCR) when identifying patients with proteinuria as it has greater sensitivity.
For quantification and monitoring of proteinuria, PCR can be used as an alternative,
although ACR is recommended in diabetics.
Urine reagent strips are not recommended unless they express the result as an ACR
Approximate equivalent values
ACR (mg/mmol) PCR (mg/mmol) Urinary protein excretion (g/24 h)
30 50 0.5
70 100 1
Collecting an ACR sample:
by collecting a 'spot' sample it avoids the need to collect urine over a 24 hour
period in order to detect or quantify proteinuria
should be a first-pass morning urine specimen
if the initial ACR is > 30 mg/mmol and < 70 mg/mmol, confirm by a subsequent early
morning sample. If the initial ACR is > 70 mg/mmol a repeat sample need not be
tested
Interpreting the ACR results:
in non-diabetics an ACR > 30 mg/mmol is considered clinically significant
proteinuria
in diabetics microalbuminuria (ACR > 2.5 mg/mmol in men and ACR > 3.5 mg/mmol
in women) is considered clinically significant
BP targets
CKD with proteinuria ACR ≥70 mg/mmol or diabetes ---- blood pressure target < 130/80
mmHg.
The NICE guidelines recommend that a blood pressure target < 140/90 mmHg should
be used in non-diabetic patients with CKD and an ACR <70 mg/mmol.
NOT for lower systolic (<120 mmHg) or diastolic (<60 mmHg)
2
, Haematuria
The management of patients with haematuria is often difficult due to the absence of
widely followed guidelines.
It is sometimes unclear whether patients are best managed in primary care, by
urologists or by nephrologists.
The terminology surrounding haematuria is changing.
Microscopic or dipstick positive haematuria is increasingly termed non-visible
haematuria
whilst macroscopic haematuria is termed visible haematuria
Non-visible haematuria is found in around 2.5% of the population.
Causes of transient or spurious non-visible haematuria
UTI
menstruation
sexual intercourse
vigorous exercise (this normally settles after around 3 days)
Spurious causes - red/orange urine, where blood is not present on dipstick
foods: beetroot, rhubarb
drugs: rifampicin, doxorubicin, Metronidazole
Causes of persistent non-visible haematuria
1) cancer (bladder, renal, prostate)
2) stones
3) benign prostatic hyperplasia
4) prostatitis
5) urethritis e.g. Chlamydia
6) renal causes: IgA nephropathy, thin basement membrane disease
Management:
Current evidence does not support screening for haematuria.
The incidence of non-visible haematuria is similar in patients taking aspirin/warfarin to
the general population hence these patients should also be investigated.
Testing
1) urine dipstick is the test of choice for detecting haematuria
persistent non-visible haematuria is often defined as blood being present in 2 out of
3 samples tested 2-3 weeks apart
2) BP , RFTs, and albumin:creatinine (ACR) or protein:creatinine ratio (PCR) should also
be checked
3) urine microscopy may be used but time to analysis significantly affects the number of
RBCs detected
3
, NICE urgent cancer referral guidelines
1) of any age with painless macroscopic haematuria
2) patients under the age of 40 years with normal renal function, no proteinuria and who
are normotensive do not need to be referred and may be managed in primary care
3) aged 40 years and older who present with recurrent or persistent UTI associated with
haematuria
4) aged 50 years and older who are found to have unexplained microscopic haematuria
4
