Medical Management of Renal Artery Stenosis

Renal artery stenosis is a condition that requires medical management to control hypertension. Even if the arteries are treated successfully with angioplasty, antihypertensive therapy should be initiated. The ideal agent for this purpose is one that blocks the renin-angiotensin-aldosterone system, such as angiotensin-converting enzyme (ACE) inhibitors or angiotensin-receptor blockers (ARBs). Warfarin is not indicated in patients with renal artery stenosis, but may be used for prophylaxis of embolisation in other conditions. Clopidogrel is not indicated for hypertension management in renal artery stenosis. Statins may be used for primary prevention of cardiovascular disease if cholesterol levels are raised, but controlling blood pressure is the primary consideration in renal artery stenosis. Spironolactone should not be used in patients with renal compromise. Control of blood pressure should ideally be achieved using ACE inhibitors or ARBs.

Functions of the Proximal Convoluted Tubule in the Nephron

The proximal convoluted tubule (PCT) is a crucial part of the nephron, responsible for several important functions. One of its primary roles is the reabsorption of sodium, which occurs through active transport facilitated by the numerous mitochondria in the epithelial cells. This creates a concentration gradient that allows for the passive reabsorption of water. Glucose is also reabsorbed in the PCT through secondary active transport, driven by the sodium gradient. The PCT also regulates the pH of the filtrate by exchanging hydrogen ions for bicarbonate ions. Additionally, the PCT is the primary site for ammoniagenesis, which involves the breakdown of glutamine to α-ketoglutarate. Finally, the regulation of urine concentration occurs in the distal convoluted tubule and collecting duct under the influence of vasopressin.

Breastfeeding has some contraindications that are important to know, especially when it comes to drugs. Antibiotics like penicillins, cephalosporins, and trimethoprim are safe for breastfeeding mothers, as are endocrine drugs like glucocorticoids (in low doses) and levothyroxine. Epilepsy drugs like sodium valproate and carbamazepine, asthma drugs like salbutamol and theophyllines, and hypertension drugs like beta-blockers and hydralazine are also safe. Anticoagulants like warfarin and heparin, as well as digoxin, are also safe. However, some drugs should be avoided, such as antibiotics like ciprofloxacin, tetracycline, chloramphenicol, and sulphonamides, psychiatric drugs like lithium and benzodiazepines, aspirin, carbimazole, methotrexate, sulfonylureas, cytotoxic drugs, and amiodarone. Other contraindications include galactosaemia and viral infections, although the latter is controversial in the developing world due to the increased risk of infant mortality and morbidity associated with bottle feeding.

Managing a Patient with Suspected Chronic Kidney Disease

When a patient presents with suspected chronic kidney disease (CKD), it is important to perform a thorough examination and urinalysis to confirm the diagnosis. While patients with CKD stages 1-3 may not exhibit symptoms, those in stages 4-5 may experience endocrine/metabolic derangements or disturbances in water or electrolyte balance. Anaemia is often one of the first signs of CKD, but the lack of physical findings on examination does not exclude kidney disease. Initial screening for proteinuria can be done with a standard urine dipstick, and further testing may be necessary if the test is positive. Referral to a nephrology outpatient may be necessary, depending on the severity of the CKD. ACE inhibitors should only be started once the patient’s baseline renal function has been established, and blood tests should be rechecked in 2 weeks. Immediate admission is only necessary for patients with CKD stage 5 who present with acute indications for dialytic therapy.

Common Kidney Disorders and Their Symptoms

Renal cell carcinoma (RCC), renal tract calculi, autosomal dominant polycystic kidney disease (ADPKD), renal amyloidosis, and reflux nephropathy are some of the common kidney disorders. RCC is the most prevalent type of kidney cancer in adults, and it may remain asymptomatic for most of its course. Renal tract calculi cause sudden onset of severe pain in the flank and radiating inferiorly and anteriorly. ADPKD is a multisystemic disorder characterised by cyst formation and enlargement in the kidney and other organs. Renal amyloidosis is caused by extracellular and/or intracellular deposition of insoluble abnormal amyloid fibrils that alter the normal function of tissues. Reflux nephropathy is characterised by renal damage due to the backflow of urine from the bladder towards the kidneys.

Hyponatraemia and hypokalaemia are caused by bendroflumethiazide, while spironolactone is linked to hyperkalaemia. Smoking would only be significant if the patient had lung cancer that resulted in syndrome of inappropriate ADH secretion, but there is no evidence of this in the given scenario.

Thiazide diuretics are medications that work by blocking the thiazide-sensitive Na+-Cl− symporter, which inhibits sodium reabsorption at the beginning of the distal convoluted tubule (DCT). This results in the loss of potassium as more sodium reaches the collecting ducts. While loop diuretics are better for reducing overload, thiazide diuretics have a role in the treatment of mild heart failure. Bendroflumethiazide was commonly used for managing hypertension, but recent NICE guidelines recommend other thiazide-like diuretics such as indapamide and chlortalidone.

Like any medication, thiazide diuretics have potential adverse effects. Common side effects include dehydration, postural hypotension, and electrolyte imbalances such as hyponatraemia, hypokalaemia, and hypercalcaemia. Gout, impaired glucose tolerance, and impotence are also possible. Rare adverse effects include thrombocytopaenia, agranulocytosis, photosensitivity rash, and pancreatitis.

To manage hypertension, current NICE guidelines recommend using thiazide-like diuretics such as indapamide or chlortalidone as first-line treatment. If blood pressure is not adequately controlled, a calcium channel blocker or ACE inhibitor can be added. If blood pressure remains high, a thiazide-like diuretic can be combined with a calcium channel blocker or ACE inhibitor. In some cases, a beta-blocker or aldosterone antagonist may also be added. Regular monitoring and adjustment of medication is necessary to ensure optimal blood pressure control.

The Renal Tubules: Functions and Regulation

The kidneys play a crucial role in maintaining the body’s fluid and electrolyte balance. This is achieved through the intricate workings of the renal tubules, which are responsible for filtering and reabsorbing various substances from the blood.

Vasopressin, also known as antidiuretic hormone, regulates water excretion in the distal convoluted tubule and collecting ducts. Its receptor, vasopressin 2, triggers the insertion of aquaporin-2 channels, allowing water to be reabsorbed down an osmotic gradient.

The distal convoluted tubule regulates pH by absorbing bicarbonate and secreting protons, as well as controlling sodium and potassium levels through aldosterone-mediated ion transport. It also participates in calcium regulation by reabsorbing it in response to parathyroid hormone.

The proximal convoluted tubule reabsorbs the majority of ions and water in the urinary space back into the body.

The ascending limb of the loop of Henle is impermeable to water, but actively reabsorbs sodium, potassium, and chloride ions. This generates a positive electrochemical potential difference in the lumen, driving more paracellular reabsorption of sodium and other cations.

The collecting ducts continue the work of water reabsorption and electrolyte balance initiated in the collecting tubules. Progenitor cells within the collecting duct epithelium respond to tubular injury by proliferating and expanding the principal cell population to maintain epithelial integrity, or by committing to a myofibroblastic phenotype and forming peritubular collars in response to increased intraluminal pressure.

This expectant woman displays indications that align with a urinary tract infection. According to the BNF, trimethoprim should not be used during the initial trimester as it can hinder folate. Ciprofloxacin is not recommended for use during pregnancy. Since the patient is clearly experiencing a UTI and has a fever, prompt treatment is necessary instead of waiting for the MSU.

Urinary tract infections (UTIs) are common in adults and can affect different parts of the urinary tract. The management of UTIs depends on various factors such as the patient’s age, gender, and pregnancy status. For non-pregnant women, local antibiotic guidelines should be followed if available. Trimethoprim or nitrofurantoin for three days are recommended by NICE Clinical Knowledge Summaries. However, if the patient is aged over 65 years or has visible or non-visible haematuria, a urine culture should be sent. Pregnant women with UTIs should be treated with nitrofurantoin, amoxicillin, or cefalexin for seven days. Trimethoprim should be avoided during pregnancy as it is teratogenic in the first trimester. Asymptomatic bacteriuria in pregnant women should also be treated to prevent progression to acute pyelonephritis. Men with UTIs should be offered a seven-day course of trimethoprim or nitrofurantoin unless prostatitis is suspected. A urine culture should be sent before antibiotics are started. Catheterised patients should not be treated for asymptomatic bacteria, but if symptomatic, a seven-day course of antibiotics should be given. Acute pyelonephritis requires hospital admission and treatment with a broad-spectrum cephalosporin or quinolone for 10-14 days. Referral to urology is not routinely required for men who have had one uncomplicated lower UTI.

Appropriate Referrals and Investigations for Patients with Haematuria

Haematuria, or blood in the urine, can be a sign of underlying bladder cancer. According to The National Institute for Health and Care Excellence guidelines, patients aged over 45 years with unexplained visible haematuria should be urgently referred for potential bladder cancer. Additionally, patients over 60 years with unexplained non-visible haematuria and either dysuria or a raised white cell count on a blood test should also be referred urgently.

An ultrasound scan might be arranged by the secondary care team for investigation of the bleeding from the renal tract. However, arranging this as an initial investigation through primary care could delay diagnosis. A 2-week wait ‘cancer exclusion’ referral would be more appropriate.

A cystoscopy might be arranged as part of the investigation, but this should be arranged via the hospital team after the patient has been referred via the 2-week-wait pathway. Arranging an outpatient cystoscopy as a first-line investigation would be inappropriate since it could lead to a delay in diagnosis.

Starting oral antibiotics would not help the patient, as her urine dip is negative for infection. Antibiotics could be considered if she had presented with symptoms or signs of infection such as dysuria, frequency or burning on urination. Frank haematuria which presents without symptoms of infection may be suggestive of bladder cancer, therefore she needs to be referred for further investigation.

Distinguishing between Acute Kidney Injury and Chronic Kidney Disease

One of the most effective ways to differentiate between acute kidney injury (AKI) and chronic kidney disease (CKD) is through the use of renal ultrasound. In most cases, patients with CKD will have small kidneys that are bilateral. However, there are some exceptions to this rule, including individuals with autosomal dominant polycystic kidney disease, diabetic nephropathy in its early stages, amyloidosis, and HIV-associated nephropathy.

In addition to renal ultrasound, there are other features that can suggest CKD rather than AKI. For example, individuals with CKD may experience hypocalcaemia due to a lack of vitamin D. By identifying these distinguishing factors, healthcare professionals can more accurately diagnose and treat patients with kidney disease. Proper diagnosis is crucial, as the treatment and management of AKI and CKD differ significantly.