We study complete finite topology immersed surfaces Σ in complete Riemannian 3-manifolds N with sectional curvature K N ≤ −a 2 ≤ 0, such that the absolute mean curvature function of Σ is bounded from above by a and its injectivity radius function is not bounded away from zero on each of its annular end representatives. We prove that such a surface Σ must be proper in N and its total curvature must be equal to 2πχ(Σ). If N is a hyperbolic 3-manifold of finite volume and Σ is a properly immersed surface of finite topology with nonnegative constant mean curvature less than 1, then we prove that each end of Σ is asymptotic (with finite positive multiplicity) to a totally umbilic annulus, properly embedded in N .Mathematics Subject Classification: Primary 53A10, Secondary 49Q05, 53C42. Key words and phrases: Calabi-Yau problem, hyperbolic 3-manifolds, asymptotic injectivity radius, bounded mean curvature, isoperimetric inequality. Definition 1.1. Let e be an end of a complete Riemannian surface Σ whose injectivity radius function we denote by I Σ : Σ → (0, ∞). Let E(e) be the collection of proper subdomains E ⊂ Σ, with compact boundary, that represents e. We define the (lower) asymptotic injectivity radius of e byNote that if Σ has an end e which admits a one-ended representative E, then I ∞ Σ (e) = lim inf E I Σ | E . If Σ has finite topology, then every end of Σ has a one-ended representative which is an annulus (i.e., a surface with the topology of S 1 × [0, ∞)), hence this simpler definition can be used. Moreover, Lemma 5.1 in the Appendix shows that if Σ has nonpositive Gaussian curvature and an end e has a representative E which is an annulus, then for every divergent sequence of points {p n } n∈N on E,We define the mean curvature function of an immersed two-sided surface Σ with a given unit normal field in a Riemannian 3-manifold to be the pointwise average of its principal curvatures; note that if Σ does not have a unit normal field, then the absolute value |H Σ | of the mean curvature function of Σ still makes sense because a unit normal field locally exists on Σ and under a change of this local choice, the principal curvatures change sign.Theorem 1.2. Let N be a complete 3-manifold with sectional curvature K N ≤ −a 2 ≤ 0, for some a ≥ 0. Let ϕ : Σ → N be an isometric immersion of a complete surface Σ with finite topology, whose mean curvature function satisfies |H ϕ | ≤ a. Then Σ has nonpositive Gaussian curvature and the following hold:A. If N is simply connected, then I ∞ Σ (e) = ∞ for every end e of Σ.B. If N has positive injectivity radius Inj(N ) = δ > 0, then every end e of Σ satisfies I ∞ Σ (e) ≥ δ. In particular, Σ has positive injectivity radius.C. If I Σ is bounded, then Σ has finite total curvature Σ K Σ = 2πχ(Σ), where χ(Σ) is the Euler characteristic of Σ. Furthermore, for each annular end representative E of Σ, the induced map ϕ * : π 1 (E) → π 1 (N ) on fundamental groups is injective.