9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis

ABIM Internal Medicine Exam

Track your progress as you read

Finished sections get a check mark.

1 Chapter 0: The ABIM Exam, Blueprint & Study Strategy

0.1 Exam Format, Question Types & the 2026 Blueprint 0.2 Eligibility, Registration, Fees & Exam-Day Logistics 0.3 Scoring, the Passing Standard & Score Reports 0.4 Building a Blueprint-Weighted Study Plan

2 Chapter 1: Cardiovascular Disease (14% of Exam)

1.1 Ischemic Heart Disease & Acute Coronary Syndromes 1.2 Antithrombotic Therapy, Secondary Prevention & Mechanical Complications of MI 1.3 Atrial Fibrillation, Atrial Flutter & Stroke Prevention 1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias 1.5 Heart Failure: Classification, Staging & Guideline-Directed Medical Therapy 1.6 Device Therapy, HFpEF & the Cardiomyopathies 1.7 Valvular Heart Disease & Endocarditis Prophylaxis 1.8 Pericardial Disease & Acute Aortic Syndromes 1.9 Hypertension: Classification, Diagnosis & Secondary Causes 1.10 Hypertensive Crises & Dyslipidemia 1.11 Adult Congenital Heart Disease & Coarctation of the Aorta 1.12 Syncope: Reflex, Orthostatic & Cardiac Causes 1.13 Cardiac Physical Examination, Murmurs & Antithrombotic Selection

3 Chapter 2: Endocrinology, Diabetes & Metabolism (9% of Exam)

2.1 Diabetes Mellitus: Diagnosis, Glycemic Targets & Pharmacotherapy 2.2 Insulin Therapy, Hyperglycemic Emergencies & Chronic Complications 2.3 Thyroid Function Testing & Hypothyroidism 2.4 Thyrotoxicosis, Thyroid Storm & Thyroid Nodules 2.5 Adrenal & Pituitary Disorders 2.6 Hypercalcemia, Hypocalcemia & Disorders of Mineral Metabolism 2.7 Osteoporosis & Paget Disease of Bone 2.8 Ovarian, Testicular & Reproductive Endocrine Disorders 2.9 Hypoglycemia, Endocrine Tumors, Polyglandular Syndromes & Severe Hypertriglyceridemia

4 Chapter 3: Gastroenterology & Hepatology (9% of Exam)

3.1 Esophageal Disease 3.2 Stomach & Duodenal Disease and Gastrointestinal Hemorrhage 3.3 Inflammatory Bowel Disease 3.4 Celiac Disease & Irritable Bowel Syndrome 3.5 Diverticular Disease & Colorectal Cancer Screening 3.6 Viral Hepatitis, Steatotic & Alcohol-Associated Liver Disease 3.7 Cirrhosis & the Complications of Portal Hypertension 3.8 Acute Pancreatitis 3.9 Chronic Pancreatitis & Biliary Tract Disease 3.10 Inherited, Autoimmune & Drug-Induced Liver Disease 3.11 Small Intestinal Disease, Ischemia & Gastrointestinal Complications of HIV

5 Chapter 4: Infectious Disease (9% of Exam)

4.1 Lower Respiratory Tract Infections & Sepsis Syndromes 4.2 Viral Respiratory Pathogens & Tuberculosis 4.3 Central Nervous System Infections 4.4 Skin, Soft Tissue, Bone & Joint Infections 4.5 Infective Endocarditis & Cardiovascular Infection 4.6 Clostridioides difficile & Catheter-Related Bloodstream Infection 4.7 HIV Diagnosis, Antiretroviral Therapy & Prevention 4.8 Opportunistic Infections & Sexually Transmitted Infections 4.9 Fever of Unknown Origin, Neutropenic Fever & Toxic Shock 4.10 Travel-Related Illness, Vector-Borne Disease & Outbreaks 4.11 Infection Prevention, Nosocomial Infection & Postexposure Prophylaxis 4.12 Rheumatic Fever, Poststreptococcal Disease, Enteric & Hepatic Infections

6 Chapter 5: Pulmonary Disease (9% of Exam)

5.1 COPD: Diagnosis, GOLD Classification & Initial Pharmacotherapy 5.2 Interventions That Reduce COPD Mortality & Exacerbation Management 5.3 Asthma: Diagnosis, Stepwise Therapy & Status Asthmaticus 5.4 Interstitial Lung Disease & Idiopathic Pulmonary Fibrosis 5.5 Sarcoidosis, Hypersensitivity Pneumonitis & Occupational Lung Disease 5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation 5.7 Pulmonary Hypertension & Sleep-Disordered Breathing 5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation 5.9 Pleural Disease, Empyema & Pneumothorax 5.10 Bronchiectasis, Cystic Fibrosis & Restrictive Lung Disease 5.11 Evaluation of Cough, Dyspnea, Hemoptysis & the Solitary Pulmonary Nodule

7 Chapter 6: Rheumatology & Orthopedics (9% of Exam)

6.1 Rheumatoid Arthritis: Diagnosis & Systemic Manifestations 6.2 Antirheumatic Pharmacotherapy & the Spondyloarthropathies 6.3 Gout: Pathophysiology & Acute Management 6.4 Urate-Lowering Therapy & Calcium Pyrophosphate Deposition Disease 6.5 Osteoarthritis 6.6 Systemic Lupus Erythematosus 6.7 Systemic Sclerosis, Sjogren Syndrome & Inflammatory Myopathies 6.8 The Vasculitides 6.9 Regional Musculoskeletal Syndromes, Back Pain & Sports Injuries 6.10 Other Primary Rheumatic Disorders & Mixed Connective Tissue Disease 6.11 Osteonecrosis & Metabolic Bone Disease

8 Chapter 7: Hematology (6% of Exam)

7.1 Approach to Anemia & the Microcytic Anemias 7.2 Macrocytic, Normocytic & Hemolytic Anemias 7.3 Hemoglobinopathies, Thalassemias & Paroxysmal Nocturnal Hemoglobinuria 7.4 Platelet Disorders, Thrombocytopenia & the Bleeding Patient 7.5 Coagulation Factor Disorders, Thrombophilia & Anticoagulant Reversal 7.6 Acute Leukemias, Chronic Leukemias & Myeloproliferative Neoplasms 7.7 Lymphomas & Plasma Cell Disorders 7.8 Myelodysplastic Syndrome, Myeloproliferative Neoplasms & Porphyria 7.9 Transfusion Medicine & Late Complications of Transplantation

9 Chapter 8: Medical Oncology (6% of Exam)

8.1 Breast, Lung, Colorectal & Prostate Cancer 8.2 Oncologic Emergencies 8.3 Genitourinary & Gynecologic Malignancies 8.4 Head and Neck, Bone & Soft Tissue Cancer and Cancer of Unknown Primary 8.5 Complications of Cancer & Its Treatment 8.6 Cancer Prevention, Survivorship & Psychosocial Care

10 Chapter 9: Nephrology & Urology (6% of Exam)

9.1 Acute Kidney Injury: Staging, Etiology & Urine Microscopy 9.2 Glomerular Disorders & Nephrotic Syndrome 9.3 Nephritic Syndromes, RPGN & Indications for Renal Replacement Therapy 9.4 Chronic Kidney Disease: Staging & Progression Retardation 9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis 9.6 Hyponatremia, Hypernatremia & Water Balance 9.7 Potassium Disorders & Systematic Acid-Base Analysis 9.8 Renal Tubular Acidosis & Nephrolithiasis 9.9 Prostate Disorders, Urinary Incontinence & Other Urologic Conditions 9.10 Cystic Kidney Disease, Obstructive Uropathy, Tubulointerstitial Disease & Hematuria

11 Chapter 10: Neurology (4% of Exam)

10.1 Acute Ischemic Stroke: Syndromes & Reperfusion 10.2 Transient Ischemic Attack, Secondary Prevention & Hemorrhagic Stroke 10.3 Headache & Facial Pain 10.4 Seizures, Epilepsy & Movement Disorders 10.5 Multiple Sclerosis & Neuromuscular Junction Disorders 10.6 Motor Neuron Disease & Acute Peripheral Neuropathy 10.7 Cranial Neuropathies & Neuro-Ophthalmology 10.8 Peripheral Neuropathies, CNS Tumors & Other Neurologic Disorders

12 Chapter 11: Psychiatry & Behavioral Health (4% of Exam)

11.1 Major Depressive Disorder & Medical Mimics 11.2 Antidepressant Pharmacotherapy & Treatment-Resistant Depression 11.3 Bipolar Disorder, Mood Stabilizers & Lithium Toxicity 11.4 Anxiety, Stress-Related & Obsessive-Compulsive Disorders 11.5 Alcohol Use Disorder & Withdrawal 11.6 Pharmacotherapy for Alcohol & Opioid Use Disorder 11.7 Toxidromes, Psychiatric Emergencies & Suicide Risk Assessment 11.8 Psychotic, Somatic Symptom, Factitious & Personality Disorders 11.9 Eating Disorders, Sleep Disorders & Sexual Health

13 Chapter 12: Dermatology (3% of Exam)

12.1 Dermatitis, Papulosquamous & Inflammatory Dermatoses 12.2 Acne, Rosacea & Cutaneous Infections 12.3 Herpes Zoster & Autoimmune Blistering Diseases 12.4 Nodules, Tumors & Cutaneous Oncology 12.5 Dermatologic Emergencies & Severe Cutaneous Adverse Reactions 12.6 Pigment Disorders, Alopecia, Nail Disease & Photosensitivity 12.7 Vascular Dermatoses, Environmental Injury & Cutaneous Signs of Systemic Disease

14 Chapter 13: Obstetrics & Gynecology / Women's Health (3% of Exam)

13.1 Contraception, Preconception Care & Teratogenicity 13.2 Hypertensive Disorders of Pregnancy & Gestational Diabetes 13.3 Thyroid Disease & Venous Thromboembolism in Pregnancy 13.4 Menopause & Menopausal Hormone Therapy 13.5 Abnormal Uterine Bleeding, Endometrial Disease & Gynecologic Cancer Screening 13.6 Breast Disorders & Diseases of the Vulva and Vagina 13.7 Menstrual Disorders, Fibroids, Endometriosis & Early Pregnancy Complications

15 Chapter 14: Geriatric Syndromes (3% of Exam)

14.1 Comprehensive Geriatric Assessment & Frailty 14.2 Falls, Gait Assessment & Polypharmacy 14.3 Urinary Incontinence & Pressure Injuries in Older Adults 14.4 Mild Cognitive Impairment, Dementia & Its Subtypes 14.5 Delirium & the Pharmacotherapy of Cognitive Disorders 14.6 Palliative Care, Hospice & Advance Care Planning 14.7 Chronic Wounds, Nutrition, Swallowing, Constipation & Hip Fracture 14.8 Sensory Impairment, Dizziness, Elder Mistreatment & Care Settings

16 Chapter 15: Allergy & Immunology (2% of Exam)

15.1 Anaphylaxis: Recognition & Emergency Management 15.2 Urticaria & Angioedema 15.3 Drug Allergy, Desensitization & Adult Immunodeficiency 15.4 Food Allergy, Insect Venom Hypersensitivity, Serum Sickness & Contrast Reactions 15.5 Rhinitis, Conjunctivitis, Eosinophilic & Mast Cell Disorders

17 Chapter 16: Preventive Medicine, Immunization & Clinical Epidemiology

16.1 The USPSTF Framework & Evidence-Based Cancer Screening 16.2 Cardiovascular & Metabolic Screening and Primary Prevention 16.3 Adult Immunization & Vaccines in Special Populations 16.4 Clinical Epidemiology, Biostatistics & Study Design

18 Chapter 17: Miscellaneous - Ethics, Patient Safety & Quality Improvement (2% of Exam)

17.1 Principles of Bioethics & Decisional Capacity 17.2 Informed Consent, Treatment Refusal & Special Scenarios 17.3 Surrogate Decision-Making, Advance Directives & Confidentiality 17.4 Patient Safety Science, Medical Error & Diagnostic Reasoning 17.5 Quality Improvement Methods, Health Disparities & Health Equity

19 Chapter 18: Perioperative Medicine & Medical Consultation

18.1 Preoperative Cardiovascular Risk Assessment 18.2 Preoperative Pulmonary Risk & Perioperative Medication Management 18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications

20 Chapter 19: Ophthalmology (1% of Exam)

19.1 The Acute Red Eye & Ophthalmic Emergencies 19.2 Painless Vision Loss & Chronic Ophthalmic Disease 19.3 Uveitis, Scleritis & Orbital Disease

21 Chapter 20: Otolaryngology & Dental Medicine (1% of Exam)

20.1 Dizziness, Vertigo & Epistaxis 20.2 Ear Disorders, Hearing Loss & Upper Respiratory Infections 20.3 Oral Cavity, Salivary Gland, Laryngeal & Taste and Smell Disorders

9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis

Key Takeaways Explain This Topic AI

Chronic kidney disease-mineral and bone disorder is enumerated under disorders of calcium metabolism and bone as well as under nephrology.

Iron stores must be repleted before starting an erythropoiesis-stimulating agent, and hemoglobin is not normalized because higher targets increase stroke and death.

Non-calcium-based phosphate binders are preferred when vascular calcification is present or calcium load is a concern.

Sodium bicarbonate to correct metabolic acidosis slows progression and preserves muscle mass in advanced disease.

Vein preservation in the non-dominant arm should begin well before dialysis is needed so that arteriovenous fistula creation remains possible.

Last updated: August 2026

1. Anemia of Chronic Kidney Disease

Anemia in CKD is typically normocytic, normochromic, and hypoproliferative, developing predictably once eGFR declines below 45–60 mL/min/1.73m2.

Pathophysiology

Relative Erythropoietin (EPO) Deficiency: Interstitial peritubular fibroblasts in the renal cortex become fibrotic and unable to synthesize adequate erythropoietin in response to hypoxia.

Functional Iron Deficiency (Hepcidin Excess): Chronic systemic inflammation in CKD upregulates hepatic Hepcidin production. Hepcidin binds to and degrades Ferroportin (the sole cellular iron exporter on enterocytes and macrophages), trapping iron in storage sites and preventing bone marrow utilization for erythropoiesis.

Uremic Toxins: Shorten red blood cell lifespan from 120 days to 60–90 days.

Evaluation & Iron Repletion Targets

Initial Workup: Complete Blood Count (CBC), absolute reticulocyte count, Serum Ferritin, Transferrin Saturation (TSAT = [Serum Iron / TIBC] x 100), Vitamin B12, Folate, and TSH.

Iron Repletion Goals (KDIGO):

Target Ferritin > 100 ng/mL in non-dialysis CKD ( > 200 ng/mL in hemodialysis CKD).

Target TSAT > 20% (optimally 20–30%).

Route of Administration:

Oral Iron (Ferrous sulfate, Ferrous gluconate, Ferric citrate): Trial in non-dialysis CKD; poorly absorbed due to elevated hepcidin and causes GI intolerance.

Intravenous Iron (Ferric carboxymaltose, Iron sucrose, Ferumoxytol): Preferred when TSAT <=20% or ferritin <=100–200 ng/mL, if oral iron fails, or in all patients on maintenance hemodialysis.

Erythropoiesis-Stimulating Agents (ESAs) & Safety Limits

Agents: Short-acting Epoetin alfa (Procrit, Epogen) or long-acting Darbepoetin alfa (Aranesp) or Methoxy polyethylene glycol-epoetin beta (Mircera).

Initiation Threshold: Initiate ESA therapy only when Hemoglobin is < 10.0 g/dL , and only AFTER iron stores are fully repleted (TSAT >20%, Ferritin >100–200 ng/mL).

Target Hemoglobin Range: 10.0 to 11.5 g/dL .

Black Box Warning & Landmark Trials (TREAT, CHOIR, CREATE): NEVER target a normal hemoglobin level (>11.5–12.0 g/dL or >13.0 g/dL) . The TREAT and CHOIR randomized controlled trials demonstrated that aggressive ESA dosing to achieve normal hemoglobin levels resulted in a significant increase in fatal and non-fatal stroke (almost 2-fold in TREAT), venous and arterial thromboembolism, vascular access thrombosis, refractory hypertension, and all-cause mortality without improving survival.

2. CKD-Mineral and Bone Disorder (CKD-MBD)

CKD-MBD is a systemic disorder of mineral and bone metabolism characterized by biochemical abnormalities (calcium, phosphorus, PTH, FGF-23, vitamin D), bone alterations (osteodystrophy), and soft tissue / vascular calcification.

• Pathophysiologic Sequence Decreased GFR (<60 mL/min)
• │
• ▼
• Phosphate Retention (Hyperphosphatemia)
• │
• ├──────────────────────────┐
• ▼ ▼
• Stimulates Osteocytes Directly Lowers Ionized Calcium
• to Secrete FGF-23 (Calcium x Phosphate Binding)
• │ │
• ▼ │
• FGF-23 Suppresses Renal │
• 1-Alpha-Hydroxylase (CYP27B1) │
• │ │
• ▼ │
• Decreased 1,25-(OH)2 Vitamin D │
• (Calcitriol Deficiency) │
• │ │
• ▼ │
• Decreased Gut Calcium Absorption │
• │ │
• └───────────┬──────────────┘
• │
• ▼
• Systemic Hypocalcemia
• │
• ▼
• Massive Stimulation of Parathyroid Glands
• │
• ▼
• SECONDARY HYPERPARATHYROIDISM (High PTH)
• │
• ┌─────────────────┴─────────────────┐
• ▼ ▼
• High-Turnover Bone Disease Extensive Medial Vascular
• (Osteitis Fibrosa Cystica) & Valvular Calcification
• Management of CKD-MBD

Therapeutic Target Modality / Pharmacotherapy Mechanism & Key Instructions

1. Hyperphosphatemia Dietary Phosphate Restriction (800–1000 mg/day) Eliminate processed foods, sodas, and inorganic phosphate food preservatives (which have 90–100% intestinal absorption compared to 40–60% for organic plant/meat phosphates).

Non-Calcium-Based Phosphate Binders (Preferred) :; • Sevelamer Carbonate (800–1600 mg PO TID with meals); • Lanthanum Carbonate (500–1000 mg PO TID chewed with meals) Bind dietary phosphate in gut lumen; preferred first-line to minimize exogenous calcium loading, slowing progressive vascular and valvular calcification. Also lowers LDL cholesterol.

Calcium-Based Phosphate Binders :; • Calcium Acetate (PhosLo); • Calcium Carbonate Inexpensive; avoid if patient has hypercalcemia, arterial calcifications, or adynamic bone disease due to accelerated vascular calcification risk.

2. Active Vitamin D Deficiency & High PTH Active Vitamin D Sterols :; • Calcitriol (0.25–0.5 µg PO daily); • Paricalcitol (selective VDR activator) Directly suppresses PTH transcription; monitor closely as active vitamin D increases intestinal absorption of both calcium and phosphate, triggering hypercalcemia and hyperphosphatemia.

3. Secondary Hyperparathyroidism Calcimimetics :; • Cinacalcet (Sensipar, 30–90 mg PO daily); • Etelcalcetide (IV post-hemodialysis) Allosteric modulators of the Calcium-Sensing Receptor (CaSR) on parathyroid cells. Increases receptor sensitivity to extracellular calcium, suppressing PTH secretion without increasing serum calcium or phosphate (causes hypocalcemia; monitor serum Ca2+).

4. Tertiary Hyperparathyroidism Subtotal Parathyroidectomy Indicated when parathyroid hyperplasia becomes autonomous with refractory hypercalcemia, hyperphosphatemia, and PTH >800–1000 pg/mL despite maximal medical therapy.

• 3. Metabolic Acidosis & Vascular Access Preparation
• Chronic Metabolic Acidosis in CKD

Mechanism: As functional nephron mass decreases below 25%, the kidney fails to synthesize adequate ammonia (NH3) and excrete daily dietary fixed hydrogen ions (titratable acid), producing a normal or high anion gap metabolic acidosis.

Consequences: Chronic acidosis (serum bicarbonate <22 mEq/L) stimulates the ubiquitin-proteasome system causing muscle wasting (sarcopenia), accelerates osteoclastic bone resorption, and accelerates progressive GFR decline.

Management: Treat with Oral Sodium Bicarbonate (650 mg PO BID to TID; 1 g = ~12 mEq HCO3-) or Sodium Citrate (Bicitra; note: avoid citrate if receiving aluminum binders) titrated to maintain serum bicarbonate between 22 and 26 mEq/L .

Vascular Access Planning & "Save the Vein"

Timely preparation for renal replacement therapy (RRT) prevents emergency hospital admissions with temporary tunneled catheters.

Vascular Access Hierarchy:

Native Arteriovenous Fistula (AVF) (Gold Standard): Surgical anastomosis connecting an artery directly to a vein (e.g., radial-cephalic [Brescia-Cimino] or brachial-cephalic). Lowest infection rate, lowest thrombosis rate, best secondary patency, and lowest mortality. Requires 3 to 6 months to mature .

Arteriovenous Graft (AVG): Synthetic PTFE tube interposed between artery and vein. Matures faster (2–4 weeks), but significantly higher thrombosis and infection rates.

Tunneled Cuffed Catheter (Permacath): Highest rates of catheter-related bloodstream infection, central venous stenosis, and all-cause mortality. Reserve as a bridge or last resort.

Access Timing: Construct the AVF 6 to 12 months before anticipated maintenance dialysis (typically when eGFR is 15 to 20 mL/min/1.73m2, Stage G4/G5 ).

"Save the Vein" Rule: In all patients with CKD Stage G4 or G5 (eGFR <30 mL/min/1.73m2), strictly protect the non-dominant upper extremity from all peripheral venipunctures, IV line placements, and especially Peripherally Inserted Central Catheters (PICCs) . Subclavian vein catheterization is strictly contraindicated due to high rates of subclavian vein stenosis, which destroys the ipsilateral limb for future AVF/AVG creation.

Pre-Emptive Kidney Transplantation:

Transplantation provides superior long-term survival, lower cardiovascular mortality, and superior quality of life compared to maintenance dialysis.

Referral Threshold: Refer for comprehensive transplant evaluation when eGFR falls below 20 mL/min/1.73m2 (Stage G4). A pre-emptive living donor transplant (performed prior to ever starting dialysis) yields the highest graft and patient survival rates.