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    Related Topics

    From Urinary System

    Bladder Neck
    Region surrounding internal urethral orifice.
    Loop of Henle
    Creates osmotic gradient in medulla.
    Internal Urethral Orifice
    Opening from bladder to urethra.
    Proximal Convoluted Tubule
    Reabsorbs water, ions, and nutrients.
    Efferent Arteriole
    Drains from glomerulus.
    Renal Pelvis
    Funnel-shaped basin collecting urine into ureter.
    Ureteral Openings
    Where ureters drain into bladder.
    Interlobar Arteries
    Run between renal pyramids.
    Interlobular Arteries
    Extend into cortex.
    Ureteral Orifice
    Opening of ureter into bladder.
    Median Umbilical Ligament
    Remnant of embryonic urachus.
    Spongy Penile Urethra
    Longest male urethra segment.
    Ureteropelvic Junction
    Where renal pelvis becomes ureter.
    Hilum of Kidney
    Entry/exit site for vessels, nerves, and ureter.
    Ureterovesical Junction
    Ureter entry into bladder.
    Bowman’s Capsule
    Surrounds glomerulus; initial urine collection.
    Renal Artery
    Supplies oxygenated blood to kidney.
    Pelvic Ureter
    Segment within the pelvic cavity.
    Perirenal Fat
    Cushions and protects kidneys.
    Renal Fascia
    Connective tissue anchoring kidney.
    Collecting Duct
    Final site for water reabsorption.
    Urinary Bladder
    Stores urine until micturition.
    Bladder Peritoneum
    Covers superior bladder surface.
    Major Calyces
    Formed by union of minor calyces.
    Kidneys
    Primary organs for filtration, fluid balance, and excretion.

    Renal Pyramids

    Reviewed by our medical team

    Cone-shaped tissues in the medulla.

    1. Overview

    Renal pyramids are cone-shaped structures located within the renal medulla of the kidney. Each pyramid contains numerous collecting ducts, loops of Henle, and vasa recta, all of which contribute to the concentration and transport of urine. These pyramids form the core functional architecture of the renal medulla and culminate in the renal papilla, through which urine exits into the minor calyces.

    2. Location

    Renal pyramids are located:

    • Within the renal medulla, deep to the renal cortex.

    • Separated by renal columns (extensions of cortical tissue).

    • Their bases face the cortex; their apices (renal papillae) point toward the renal sinus and minor calyces.

    Each kidney typically contains 8 to 18 renal pyramids, with one pyramid draining into one minor calyx.

    3. Structure

    Renal pyramids are composed of vertically arranged tubules and vessels, giving them a striated appearance. Key components include:

    • Collecting ducts: Transport urine from nephrons to the renal papilla.

    • Loops of Henle: Extend from cortical nephrons into the medulla, playing a critical role in urine concentration.

    • Vasa recta: Capillary loops that surround the loops of Henle and collecting ducts, maintaining the medullary osmotic gradient.

    • Interstitial tissue: Supports tubular and vascular structures and contributes to solute handling.

    The apical end of each pyramid (renal papilla) opens into a minor calyx via multiple ducts (ducts of Bellini).

    4. Function

    The renal pyramids serve as a conduction and processing zone for urine. Their primary functions include:

    • Conducting urine: Transporting urine from cortical nephrons to the minor calyces.

    • Urine concentration: Facilitating water reabsorption and solute exchange through the countercurrent mechanism in the loop of Henle and vasa recta.

    • Final adjustments: Fine-tuning the composition of urine before it exits the papillae.

    5. Physiological Role(s)

    Renal pyramids play a critical role in maintaining:

    • Fluid and electrolyte balance: Through reabsorption of water, sodium, potassium, and other solutes.

    • Acid-base homeostasis: By excreting hydrogen ions and reabsorbing bicarbonate.

    • Urine osmolality: Via the countercurrent multiplier system in the loops of Henle and exchange in the vasa recta.

    • Hormonal response: Collecting ducts respond to antidiuretic hormone (ADH) and aldosterone to regulate water and sodium balance.

    6. Clinical Significance

    Medullary Sponge Kidney (MSK)

    A congenital condition characterized by cystic dilation of the collecting ducts within the renal pyramids. Features include:

    • Hematuria

    • Recurrent urinary tract infections

    • Kidney stones (nephrocalcinosis)

    Often diagnosed via intravenous urography showing a “paintbrush” appearance in the medulla.

    Papillary Necrosis

    Although centered on the renal papilla, this condition affects the distal part of the pyramids. Caused by:

    • Diabetes mellitus

    • NSAID abuse

    • Sickle cell disease

    Leads to sloughing of the papilla and impaired urine outflow.

    Nephrocalcinosis

    Calcium deposition within the pyramids (medullary nephrocalcinosis) may result from:

    • Hyperparathyroidism

    • Renal tubular acidosis

    • MSK

    Visible as medullary calcifications on imaging, especially CT and ultrasound.

    Imaging Considerations

    Renal pyramids appear:

    • Hypoechoic on ultrasound, forming a triangular pattern.

    • Low-attenuation zones on CT, especially when normal or fluid-filled.

    Disruption or asymmetry in the pyramid pattern can help diagnose renal pathology.

    Surgical Landmarks

    During nephron-sparing surgeries (e.g., partial nephrectomy), awareness of pyramid location is important to avoid damage to collecting ducts and vascular structures.

    Did you know? A nephron, the functional unit of the kidney, is responsible for filtering blood, reabsorbing vital nutrients, and secreting waste products?